Wanting to "check out" is usually a sign of depression.
Learning to control one's own thoughts is probably the most difficult thing in the world. We have so many things in our life competing for "mindshare". (Family, friends, co-workers, bosses, 24 hour news channels, Ads, spouses/significant others, and Internet articles...etc)
It helps when one knows them self well enough to know what cheers them up, motivates them, or activities they help them take their mind off of things. For some people it's reading a good book, taking a walk, working out,listening to their favorite music, or going to see a movie.
Believe it or not some people want to avoid being around "happy" people or participating in activities they normally enjoy when they're feeling "blue". They often disconnect from others in order wallow in it. They'll turn off their phones, refuse to answer the door, and so on.
Just having a small mental break can reinvigorate one into putting things in to perspective. There's always something good in our life.
It's also important to have something to "look forward to" on your calendar. When we don't everyday is the same.
The world may not owe you anything but (you) owe yourself the world!