read this before trying again: https://en.wikipedia.org/wiki/Set_and_setting
My personal rules for any LSD trip are: be in the company of others you feel comfortable being sober with (as in no drugs, not even weed or alcohol), be in a safe place or near a safe place you can get back to without much issue if things get overwhelming, relaxing music, lots of fresh fruit on hand. Oh, and make sure anyone you're with is not on any sort of anti-depressant. I've seen some bad mixes with SSRIs and psychedelics (primarily DMT).
You should be ready to go introspective during your trip. If things get overwhelming, lay down, focus on your breath, and remember you're tripping and that you will sober up in a few hours. Let yourself cry if you need to. The worst experiences come when you try to fight it.
Marijuana never caused me any panic, but at the end of the trip, I was barely feeling anything and smoked a joint, what happened next was frightening. I felt an ache at my heart and considered calling the hospital for several hours, but was scared because of intoxication. I could not relax and sit at one place, there was darkening in my eyes, and peripheral vision was gone, and LSD made the feeling of fear massively intense. It felt as if my heart was going to stop just because I was thinking so much that I was dying.
I can only name what helped me then: I started walking short distances telling myself that if I manage to go from point A to point B then I'm fine and it's just a bad drug tripped. It helped, also tasting various flavours and hearing sounds from outside the street helped me focus my attention on something else. After a few hours of walking/tasting/hearing, I noticed my heart pace slowing down and the realisation that I wasn't in any real danger followed next. A terrible feeling that I will never forget. The bad trip lasted about 6 hours, and for the next few days, I felt a sharp pain in my chest.