If we focus on a few things, it is easier for us to devote more time and effort for those things.
I do not become a good friend based on the number of my friends. I become a good friend based on the quality of those friendships. But the quality of those friendships only increase proportionally with the time and effort I devote to cultivating those friendships.
But here’s the point: I need to have fewer friends so that I can give more time to each of them.