“Bitochon” is the awareness that the Creator is running the world and all that happens is for your ultimate benefit. The more bitochon you have, the less anxiety you will experience.
When you have an internalized awareness that all that He does is for your good, you will find yourself experiencing greater degrees of inner peace and serenity.
Sources: For a series of probing questions on this topic, see Rabbi Zelig Pliskin’s “Gateway to Self Knowledge,” pp.116-8