Each person’s karmic background is really, really complex. You just trust that putting in good actions, putting in skillful actions, is going to help.

"The Buddha once said that the results of action are an imponderable, which may sound strange given that his teaching on action is so basic to all his other teachings. The main principle is simple: You do, or say, or think something with a skillful intention, and the results are going to be good; you do, or say, or think something with unskillful intentions, and the results are going to be bad. That’s simple — but the problem is that that simple principle gets iterated many, many, many times. And that makes its results complex.

How many times in the course of the day have you done something, or said something, or thought something? You can’t count all the actions, and that’s just in one day. And it spreads out over lifetimes. You begin to realize that you’ve got a lot of things going on here. Some of the actions will give results quickly; others will give them slowly. Others are ready to give the results, but you’re not watering them, so they don’t give the results. Others are a long time from giving the results. You water and water and water them, and nothing seems to happen. The complexity of the interactions among all these actions is what makes the results of action an imponderable. And this is what you bring to the meditation.

This is one of the reasons why — when people ask, “How long will it take for me to gain jhana?” or “How much longer will my meditation be miserable?” — there’s no answer. Each person’s karmic background is really, really complex. It’s not the case that what we see right now is simply the running balance in our one karma account. The Buddha’s image is of a field with lots of seeds and, as I said, some of them are ready to sprout; some are not. And who knows what unsprouted seeds are in your field?

What this means, as you come to practice meditation, is that you can’t set a timeline or a deadline for when you’re going to get the results you want. You just trust that putting in good actions, putting in skillful actions, is going to help."

~ Thanissaro Bhikkhu "Truths Noble in the Heart"