"When nothing seems to help, I go and look at a stonecutter hammering away at his rock, perhaps a hundred times without as much as a crack showing in it. Yet at the hundred and first blow it will split in two, and I know it was not that last blow that did it—but all that had gone before.” (Jacob A. Riis)
I'm not sure there's a better way to describe the power of perseverance. Whether it's exercising, learning an instrument, or any other endeavor, it is way too easy to give up early on. You can't see the crack forming, but every strike is a strike closer to the split. The tough part is that you never know when it's coming. Before you throw in the towel, remember that you could be giving up one or two strikes away from something big.
My approach? Find joy in the hammering, not the final crack.