What signs might indicate that your desire for reconciliation is more about avoiding loneliness than genuine feelings for your ex?

How do you politely tell a college classmate that you don't want to be study buddies anymore because they take too long to learn the subject matter and aren't able to keep up with you?
What are those simple things that brings you happiness? I'm trying to heal from depression after an abusive relationship, I lost my "joie de vivre" & I try to steal some crumbs of happiness. Can you inspire me?