From my point of view, getting better at something is usually the fun part. It doesn't have to be sad that I haven't reached a goal yet. Let's say your fitness goal is to do 30 pushups in a row, but you can only do 20 right now. You good choose to feel all depressed that you are 10 short of your goal, or you could be like "I've gotten to 20 so far, that is pretty awesome, it will be fun to see if I can get up to 30". Having a challenge to work on and gradually overcoming it can be really fulfilling.

You might want to consider that this attitude might account for your constant downward progress. Always being on high alert and downplaying any good is a recipe for burnout and depression. Rejoicing in the good days can give you little rays of hope that there can be more future good days and motivate you to keep working through your problems.