When Levin simply lives instead of thinks about living, everything is fine.
Levin was once consumed by the idea of serving mankind and performing great deeds for humanity, but has now realized that those ideals worked better in the abstract than in actuality.
Now that Levin confines himself to what affects himself and his family personally, he finds work much more agreeable. He doesn't feel the same joy at working on his estate that he used to, but he's gotten better at it now that he performs his chores without too much philosophy.
Levin stays busy and adheres to a strict code of conduct; this code doesn't seem to be dedicated to maximum profit.
It bothers him when he thinks about it too deeply, so instead of thinking he has decided to just live.