When it feels too much, I go back to the building where I live, and set small but realistic goals. Like, I want this block to be complete with all the questions. Then I look around and add things that aren't in the map yet, until my block is as close to complete as I can get it. An island of perfect mapping surrounded by more incomplete mapping. Only then I move on to another well defined area, preferably close to home. Maybe other people will see this example of good mapping and think "I could do that with my local area too!" My personal opinion is that OSM needs many local experts, rather than a few overwhelmed people trying to do it all for everyone else. I have my eyes on where I live, and notice changes over time.