Realize that the experience comes from within you which means that the fate of it lays in your own hands. That can be tough to see, and it can be tempting to think of it as being a victim of circumstances and causality.
For these reasons your worrying alone about a bad trip can become a self-fulfilling prophecy. The key to overcoming bad elements in a trip is accepting that not everything is perfect and positive, take the bad with the good. Look at it, don't look away, be brave and have real faith in yourself that it will be alright. That you and your trip will be alright because you will it to be.
Make sure you do it in the right set and setting, make sure there is nothing you have to do or have to NOT do - like doing it in secret hiding from your parents is no good - being responsible for something on that day, that can make other people rely on you and want you to do things like drive someone or take care of someone... all of that is no good, you need to be able to be free.
Next step is actually act free, free yourself from yourself and let everything flow naturally. Leave your thoughts about the difference between 'what is' and 'what should be' at the door, expectations can make something exciting but don't go too far with it or else there is too much pressure to just things be what they are.
Be in agreement with yourself that whatever the trip will be, it is perfect in its own right.
If you are a type of person who always wants to have something to do, like entertainment, try to let that go for once and be okay with just wandering around experiencing.
Some people have negative experiences, it is true - but they don't just happen at random - it's because it is not prepared correctly and something unexpected is allowed to happen, or people are mentally not in a good place when they start and approach it too casually. Then you can get your ass kicked by a psychedelic but if you are honest about it that is sort of what goes around comes around. Not like people deserve it but they usually do it to themselves if guidelines are not followed.
If you feel good about yourself and have enough time and place to trip, and by the way do not make your company too big, 1 other person is great but 3 total is what they call a crowd. Tripping with crowds is generally just disorienting and while it can be wacky and social, it is also unstable and complex social dynamics can result in unexpected turns.
Many people who have tripped quite a number of times realize that there is no such thing as a bad trip, there are only difficult experiences. The more you resist going through those the more torturous it is, but if you really confront it then you can learn incredible things. Just remember that you cannot die from something like LSD and just LET GO when you feel too much friction. It will be fine, I promise. Resistance is futile and it will only pull at you very hard.
Imagine a roller coaster: when it turns out to be very intense you can go screaming I wanna get off! I wanna get off! but you can't and it will only suck that much more. Instead just sit back and relax and let the ride wash over you. If you can contact that deep level where you can really surrender you may really feel like you have achieved something that stands for a lot more than it initially appears to!
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If you don't like dealing with things then this is probably not for you. Dealing with things helps you process them and put them in perspective and relieve you. It's quite healthy, therapeutic even.
The trip may turn out to begin recreationally and not get all that deep - some people just mainly get visuals and euphoria and stuff, but that doesn't mean that when something presents itself, something that just doesn't sit right in you... it can be bad not to deal with it. Because it will make you more aware of the fact that something is wrong and while that is a great opportunity to actually do something with it, it can make it extra difficult and disagreeable if you want to ignore it or run away from it.
These things are vital for growing up, maturing, developing yourself, becoming a whole person who works out inconsistencies.