A couple of people mentioned peaks and valleys. I completely agree. You seem to have already put some wrench time in, but try not to be discouraged. As others have suggested, you may want to just hire a pin tech and put the issues behind you.
Do NOT make any rash decisions like selling off games, because you will regret it.
I notice that i get discouraged most when i have projects stacking up. It's not that i cant handle them, but i work full time and im a father of 3. My time is limited, and it simply makes me anxious. Staring at a non-working pin for long periods of time can be discouraging. Try to focus on playing and enjoying the working ones until a tech can make the trip to help you.