I admit it can be hard at time. but try to talk your expectations down. If you want to become better at drawing don't expect to be decent in a month or even 6 months. Try to set a reachable goal. For instance at the end of this week I want to be better noticably at drawing straight lines.

By downgrading your expectations they become easier to accomplish and you will feel better. Only comparing to yourself and tryin to impriove from your old self will also help a lot.