Yesterday, after the (karate) class, our hanshi (head teacher, the dojo's owner) talked to us a bit about pushing forward when it's difficult. We had an endurance class and that included a few very intensive rounds when everyone comes to the point of failure - but has to keep going. He said we shouldn't allow ourselves to think of the body, of how tired we are, of how far the goal is. Don't look at the far goal all the time, he said. If you're walking up the mountain to the summit, don't look at the top, especially when you're tired - it's so far, it'll discourage you and you won't go/get there. Instead, make the steps, one after another, concentrate on the current step - and
that way you'll get there. Don't look back either, as that may bring memories of past failures - and they don't matter, what matters is what you do
now. What might also help is thinking of the next activity that is exciting, or of a reward awaiting us after we've done this current tough part. He learned it from the Japanese culture and his teacher during his decades in karate.
This life is tough at times, and we all have to be warriors deep inside to survive and succeed at our responsibilities along the way.