It is tricky to know. One danger of psychedelics that i can speak of from my own experience using them over a 17 year period is that they are really really really fun and interesting, endlessly so even, and so if you find that you like them, they can be very seductive. Not in the sense that you get addicted, but in the sense that you do drugs instead of doing other things ie. especially if you are trying to study, write/create something, make music, get qualifications, develop some personal project or meditative practice etc etc etc. I think psychedelics actually HELP most people do alot of things BETTER, especially thinking, creating, developing your visual capacities or other capacities that may have been less developed beforehand, making your mind more lateral, being passionate about something, imagining, fantasising etc....Psychedelics are generative, they complicate our intelligence and our creativity. But they also take time to buy, make, take, come down from, process, talk about, and er...go on forums to blah about....
So you just need to monitor how much of your life gets gobbled up thinking about the experience - are you happy with that level? are there things that are being sacrificed because of that choice? are you getting on with the shit that really MATTERS MOST to you. For some people, the psychedelics matter most. For me they matter, but not MOST above all else. I want them part of my life but not taking it over. Fortunately for me I type fast and process quickly.8)
But researching various psychedelics, chasing dealers (for acid), sourcing dmt and salvia, hunting mushrooms, growing mushrooms, these have been all massively time-consuming and I can only do them for a limited time. San pedro is low maintenance fortunately 
It may be that the younger you are, the more you need to manifest things in the world to secure your self-esteem - I think that was definitely true for me and that is why I am happy I did not take them at 19. But i had achieved a lot by the time I was 22 and was about to embark on a big creative project. So i didn't feel like I was up the river without a paddle but I was also ripe to have my illusions shattered and put back together again (and shattered again and...etc. etc..) So it made everything take longer than what it might have otherwise, but it meant that I massively expanded my horizons, bit off more than I could chew and so just kept chewing on it for long time afterwards...:roll: It woke me up to a kind of spiritual consciousness - opened my third eye, I guess you could say.:? I mean, in the sense that shortly after taking lots of acid over a year, I suddenly one day got passionate about a consuming daily meditative practice that I have done ever since and learnt a LOT from.
I have no regrets and am very grateful for the role of psychedelics in my life. But I am glad they are NOT ALL I AM DOING.
And so I have to monitor how much I put into thinking about them because I have other stuff I need to get done. I am in an intense processing phase at the moment because I have done a lot of acid and dmt lately. But I will be obsessed with other things now for the next however long. And then obsessed again no doubt for a few months at some point in 2010. 