I would say that before each trip, really look into how you feel. Are you happy? Introspective? Depressed? Whatever you are, you need to take that into consideration, especially if you've been tripping a lot. Personally, I would never take a psychedelic if I had felt recently traumatized, overwhelmed, stressed, or really unhappy in any way. (Although for some people acid helps them with these problems)
Know yourself, and don't lose sight of yourself. If you ever have ANY doubts about embarking on a trip, really take a breather and stop and think. If you feel out of it or too anxious or anything when you're straight, I'd say hold off and recuperate. Beyond that it seems like it's mostly gonna be your decision.