Can't help you with that, I don't have patience. What I have is something else that I don't know an English word for, we call it "sisu". Kind of stubbornness that doesn't let me give up after I have started no matter what.
So ... you are from Finland. Forgive me for not having noticed that before. Terve! I used to work with a girl named Outi at Ericsson once.
The Swedish equivalent to sisu should be "jävlaranamma", I guess. Or maybe it is more close to what an American would call "turbo boost". Or simply "determination".
Well, to go back to the original question, my recipie for overcoming that feeling of hopelessness and impatience is to go down to atom level. So, you cannot play that certain piece? OK, just don't be afraid to go into details. I have discovered that my always-so-recurring-mistakes often are caused by me being sloppy. I simply haven't identified the real problem thoroughly. WHERE do I always go wrong? Often it turns out that I make a clumsy transition between, let's say, two chords, so that I slip down on wrong keys, and then I make a quick "post correction" or just get annoyed which will affect my playing negatively.
And how do I get rid of it? Well, not by quickly playing that transition one million times more, repeating the same mistake one million times more, but by slowing down considerably. And then I make a stop RIGHT BEFORE that critical spot, make dead sure that I will hit the right keys this time, and play. Then I stop and repeat the whole procedure, and gradually I can play faster and with shorter stop, until the error is totally gone.
I do not bother about "keeping the rythm" or care too much about note values in this process, if my major issue is about playing wrong keys. It is not about making beautiful music at that stage anyway.
Of course I might also have a rythm problem, and I will take care of it once I don't play wrong notes. But I believe in solving one problem at a time.
So, my idea is that you have to take the bull by the horns (you say that in English too, don't you?) and really analyze your problem and really try to fix it. Or them ... At least my general mistake when I "just cannot learn" is that I don't dare to look in the microscope. We might call it impatience, yes. But this microscope focus also solves the impatience problem, because you will very quickly notice significant progress and that is very encouraging.
So, stop trying to play too much too fast. Break the problem down to atom level. DO NOT play wrong notes. It is better to "freeze" until you are 100 % sure you will play the right key, rather than gambling. Play so slowly that you will get it right, but don't waste time on sections you already know. (Play these faster, or not at all.)