The Buddha invites you to think about the really long term for equanimity and patience

"As the Buddha pointed out, the principle that “whatever we do, for good or for evil, to that will we fall heir” implies rebirth as well as kamma. It’s our working hypothesis. Without rebirth, the principle of kamma doesn’t jive with the facts. There are many cases in the world where people break the precepts but they get rewarded. If you were to say that actions are always rewarded in kind in this lifetime, it’s obviously not true.

So the Buddha invites you to think about the long term — and we’re talking about really long here. In his own case, in his awakening he thought back many, many lifetimes, thousands and thousands of eons — thousands and thousands of universes, actually, forming and then falling away — back so far that he said that the beginning point is not only unknowable, it’s also inconceivable. In the course of that long, long time, you’ve probably done lots of things, you’ve been lots of different beings in lots of different situations. As he said, it would be hard to find someone now who hasn’t at one point in that long time been your mother or your father, or your sister or your brother, or your son or your daughter.

Some of that past kamma has ripened and fallen to the wayside; other past actions are still giving their results. Sometimes you simply have to live with them: things about yourself you can’t change, things about the situation around you that you can’t change, things about the situation with other people who you love or hate that you can’t change.

When you take the long, long view like this, it makes a lot of your problems in your present lifetime seem pretty small. It helps give you some equanimity, gives you some patience. Because there are a lot of things in life that, if you thought, “This is your one lifetime, this is your one chance,” would strike you as very unfair. It would be hard to live with the idea that, say, someone smeared your name and you couldn’t get it un-smeared. Other people who don’t seem to have any right to power have taken over a lot of power. But if you take the long view of things, you realize that this is going to pass, and this is not your only chance. It makes it a lot easier to live with the things you can’t change, and focus on the ones you can.

You could make a case that the Buddha’s reflections on kamma are very un-American, if we define “American” as being in line with the Declaration of Independence. There’s no creator, there are no rights, and we’re not born equal. Some people are born good-looking, other people are born ugly; some people are born with a healthy body, some people with an unhealthy body. Some people are long-lived, short-lived, powerful, weak, wealthy, poor. So we come into the world not equal. But as the Buddha said, the important thing is not how you come into the world. It’s how you go out."

~ Thanissaro Bhikkhu "Patience & Hope"