relax before...

i have done shrooms twice and my last time was the scarriest thing i have ever been through. all i wanted to do was to leave my body and through up the taste i had in my stomach and mouth. my friends were watching finding nemo. i looked up at the screen and saw a shark coming after me. i ran away and went into a room where all i saw was black people (bob marley was playing in the backround). these people were telling me shit to do. i had the worst trip mainly because i wasnt relaxed and had so many things on my mind. i had my cell phone next to me the whole night. i was tripping myself out as well as my friends. have a clear head before. by the way...is it possible to end your trip? let me know