it also might be helpful to try some Pranayama Breathing techniques. These are closely associated with meditation and work well right before. They are thousand year old techniques that help to clear the mind to prepare it for deeper meditation, and relaxation of the body. I find it to sometimes work similarly to the Herb.
Google Yogananda if you are interested.

For me the idea is to rid myself of these continuous thoughts whether positive or negative. A compulsive thought is a compulsive thought. All thought are fine so long as we can evaluate them and let them run their course and ESPECIALLY let them melt into thin air. It is a lifelong practice!