Why is it that those who hardly think of themselves are always happy, while those most self-concerned can never truly celebrate anything?
Because the more space you occupy, the less room you leave for joy.
There are those who fill their entire space with self-concern. Nothing they receive, no degree of recognition, can match the space already occupied by their self-concern.
But those who make themselves small welcome everything with joy. And if once in a while life does not provide its bounty—well, if you don‘t deserve anything anyways, what is there to be depressed about?
In fact, if you feel small enough, then you rejoice when you‘re lacking too. Because small people don‘t create big issues out of things that go wrong.
Make yourself small, and there will always be room for happiness.

The keys in this fragment are small and big, as well as hapiness.. Big meaning more power, more money, more activity, while never being happy since acqusition of power or property become the goal of that person's life. The sense of sprituality is gone in that pursuit of material things ! Small, I assume it means a more measured ambition, yes, to accomplish but a mix of pursuit and spirituality. Not expecting much- one receives more precisely because not expecting.- except what comes in the way. I don't think merit is involved to receive or not receive material things because in reality there are people with no merits that appear to have "everything" but they are not happy in that pursuit. As for happiness, there is a saying: "Mi who sameach= who is happy- hasameach behelko" the one that is happy is so because he accepts his portion in life ! That leads to mental health and allows spirtuality to flourish since there is space for the pursuit of more significant issues.