I know your post is WAY old...but I wanted to answer it. I cannot believe nobody else has! The reason I found your post is by entering 'anxiety' in the search bar. I hear and understand where you are coming from in all you say. Unfortunately only ONE side (the happy trip side)gets talked about most often. I am happy that that aspect exists and it is VERY important indeed. WAY past WOW!!!! Evenso...there is another side that is yet still very important. It can seem or be very negative, but as YOU learned it(anxiety) is a knock on your door as far as what is right on top of your 'subconscious'(for lack of better term) mind and attention. You saw it and knew to correct it. Learning about ones faults and 'mindset' negativities that may be holding one back is NOT best seen on shrooms , comfortwise. As it becomes VERY large and personal. I have felt that. It CAN very easily be what your trip becomes!...a learning session that feels more like a soul-hammer.
I have had some anxiety challenges even on some low doses. (All it takes to get you in touch with some powerful parts of/in yourself, at times) Each time if I got off the 'expectation of' what I had wanted from the shroom experience and ON to what it ACTUALLY was, instead uncovering as even a negative reality in my life / inner position...I was better off for it. It can be a VERY trying adjustment!
Most recently I found my anxiety on a shroom trip to be based on my seeking such freedom and enlightenment(at whatever level)for myself, while I was ignoring the nudge I had felt for sometime to support those who were far less fortunate than me; in my normal day to day. In ignoring THAT subconscious(if not also spiritual)leading...I had created a 'poison door' that I had to travel past to get to anything beautiful. It was a bit more of a challenge than I thought. I felt in the middle of all this trip anxiety, that I was being spoken to by higher consciousness. In a subtle and yet strong enough sense to realise that this was not a trip or time for me to expect to be sensually 'entertained'...but taught. I felt I needed mercy for my selfishness and I asked for it and thanked 'them' for it! It was a hard time. Shrooms don't take you mentally AROUND what you need to face...they take you right through it....INTIMATELY.
I learned that shrooms ARE indeed going to help you learn what you NEED to learn. That the standard 'trippy trip' may just be a blessing for the less initiated or 'naive'. I DO now; very much believe that as one matures it does not remain so. That higher consciousness sought knows that YOU should know more than a 'youngster 'and is a bit more ready to challenge you. Please do not be offended by my observation(based on your age or experiences?) as it is the knowledge that was impressed upon ME. And very stongly. So much so, that I wrote down many things I was 'told' so that I would not forget. And I respected the mercy I was shown by changing my 'off-shroom' attention to better actions(in this case the charity that I had long been urged to do). I say 'mercy' toward me...because the depth of understanding (and the pain of misunderstanding )can be equally magnified during the shroom experience. You can be awed with wonder or sadness...or FEAR. BUT there is ALWAYS A REASON. I will NEVER(and it is so easy to do)ever again...'slip into' treating shrooms as an automatic 'high'. That is VERY naive and the higher planes you can go to are VERY clear and honest about YOUR OWN LOWER ONES...even when and if YOU have not been with yourself. Shrooms are NOT the dullish equivalent of a few beers(or?) to get loose and laughy. I know people who are both young and older who think so. That tells me what there shroom experience IS NOT as much as 'is'. Shrooms can take you where you are not ready to go.
You say to "not have a lot on your mind" when you do shrooms. Being with others on shrooms often mellows/blends and balances out those inner personal triggers that can get a hold of you. But then we ARE(alone/still) beings of light AND darkness(however you describe it)and you cannot expect to encounter only light or that you have an "empty mind". FEW ever really do. We are PERSONALLY adjusted or misadjusted at any given time...in whatever way within ourselves/thoughts. Some will have the bliss of ignorance(naturally or chosen)...but if you are more aware it will not be so(moreso on shrooms)for you. Who knows when?..but if you keep shrooming you WILL encounter both. Especially when you are shrooming alone. I remember several trips in a row years ago, where a segment of the trip was seeing hideous faces materialising and coming toward me. I knew I had to laugh(but not with disrespect as I knew these were telling me something I had best respect)in order to keep from being consumed in anxiety. The rest of the trip would be totally nonthreatening...but it may be just ONE element that can be YOUR scary face(s) and you need to be open to understanding. It is SO easy to freak out!!! That response will be exagerated as much as any other thing seen heard or experienced.
Anxiety is not to be taken lightly. A panic attack on shrooms is not a happy thing. If some do not learn what it is telling them and how to deal with it they should not do shrooms again UNTIL AND UNLESS they take the reasons for into serious consideration. I had a tripp that showed me I too needed to do just that.
Before I shroom, I now sit in meditation and face myself and 'those higher' with the kinowledge/humility and honesty of who I am . Consciously. When you do this, it 'pre' opens the door to what you are about to do and encounter. Better than barging in to higher realms as if your simple choice to eat a mushroom 'gives' you that 'right'? It actually does not. I have been taught(now that I am 49) that childish or naive approach is NOT acceptable, to 'those and that which' awaits. I do not take for granted the nature of those 'places and spaces' that you and I (apparently) need/choose these fruits to better reach. They can lift you higher peacefully OR by turning you inside out. People who do not know me, do not expect much from me. People who DO know me, expect more. If you want to know higher things expect higher things WILL know YOU. If you are not a shallow person...if you are spiritually awake/caring to waken, you can bet (and be ready for!)that this experience will be many things(beyond geometric patterns and enhanced sound and colors!) to help keep(or make!!) you honest. Imagine (in your conscioussitting down in a chair still and then in a few moments you found yourself on the freeway going 75 mph! If you were not really prepared for such a drastic change in mental setting and 'flow' you willl have anxiety for sure. Shrooms can throw you on the 'freeway'. Easily. I believe that honest meditation and self examination / healthy humility and calmness BEFORE one shrooms(even for 10 minutes...it is the honesty that counts)is important. You are giving over your mind basically....'wipe your feet' first. Before you go into that house. So to speak.
I do not know if I will ever go for the level 4 or 5 experience? It is not to be taken lightly I already know, from what I have experienced. I enjoy being fully present(in the non shroom way)and yet there is more to presence than this, as well. To be present with anxiety as shrooms can (also)bring the experience of, is an unfortunate(at the time!!!)and VERY uncomfortable experience for sure. Meditation OFF shrooms ,helps to balance and teach you about what is REALLY going on with you. What you think and do(not just in the moment before) when you are NOT taking mushrooms will in someway translate into your shroom experience.
thanks for posting what you experienced!