You mean you "digress?"
Diverge
intransitive verb
1. to move or extend in different directions from a common point : draw apart
2. to turn aside or deviate, as from a path, practice, or plan
They were close friends in college, but after graduation their lives diverged
A prism causes rays of light to diverge
When I started talking about my exam I diverged from the main topic at hand which was MODERN WARFARE 3!
But yeah - Digress works too!
