I had this happen too, the anxiety came back but it was because I didn't make good use of the Knowledge I was given from my many, well-driven, safe trips too. Proof that we don't have that much control and that things can go wrong later, but it did make me live a good 7 years anxiety free, being able to let go of the Fear Of The End was wonderful. In fact, I haven't tripped since 2008 and am going to do it again with Ibogaine Hcl pretty soon.
You have to accept the risks if not in the greatest mind set. I notice that tripping with other people who you feel close to who aren't prone to flipping out/will take an equal to lower dosage than you is really good in setting the mood to positive especially if you value the friend.
Don't put too much value into friends though, because 99% of men think with their cocks and who services it so if a succubus flies by and tries to steal the friend's life well there isn't much you can do.
Wow, I'm insightful yet tangential after waking up from a nightmare.