Does it help you grow?
One of the ways (and maybe the most important way) in which I evaluate whether to keep something—or someone—in my life is to ask: Does this help me grow?
If it stunts my growth, it must go. If it doesn't contribute to my growth, and thus keeps me still as time passes, then it still stunts my growth. It must go.
Do I have to read and study and practice my craft every second? No. Rest is just as important as the work itself. Entertainment falls under rest too—to rest the mind—but both only to the extent that they are needed, before they become laziness.
Bad habits. Time-consuming commitments. Excessive drinking and partying. Toxic relationships. They've been easier for me to let go of once I saw how much energy and opportunity for growth they take away.