Two things ;
1. You know it is coming, don't wait for the crash, get help now. Call your doctor, your therapist, whoever you go to to deal with this issue; and
2. This pertains only to me but I hope may help you. When I can feel the crash coming it is usually my body telling me that I need to do somethng. I try to ask myself if I am being as honest as I can be about my life. If I am not being honest with myself that dishonestly is usually the catalist for the crash. I also try to give some time to honest contemplation regarding the things in my life that have brought me here. I am still remembering childhood issues that I had forgotten about. I never deny them because they might be painful but rather look at them headon. The notion that they can't hurt you now is false in one way because they are hurting me now and true in that if I acknowledge them honestly I can see that I am not to blame or if I was, I can learn to put the blame aside because it was a long time ago.
Keep in touch,