I don't know, keeping track of accomplishments in retrospect seems to be rather an additional burden. I'd rather change the app so it helps you to pursue current goals (todos for a goal, notes etc.) and reminds you of goals you have accomplished.
I'm working on a platform which does just that. Don't really want to detract from the thread (as I appreciate the simplicity of this app in just focusing on one aspect), but the link is in my profile if you're interested.
this is an excellent point. goal-setting and achievement gives tremendous hope so that would be a most excellent feature.