When we talk about creativity, a part of it that often seems to be left out is frustration. However, frustration is an important part of the process. We don't talk about the times when frustration was so overwhelming that we wanted to quit, when we might have thought the problem was too hard to tackle. In recounting how we made a piece of music, we generally skip to how the problem was solved. The happy ending for want of a better term. The problem with this is that being annoyed, frustrated is an important part of the process. We need to be frustrated before we can find the answer, or know the question even. We need to be convinced that it's a hopeless task, to the point where we have given up and usually only then will the answer come.
Now obviously this can take many forms. You might be frustrated with a new method, or a new goal you've set yourself. However I don't think it's useful to limit this concept. We all know that art and music are way of expressing one's self. Frustration with relationships, with people that maybe you looked up to, but that have disappointed you, can be a powerful catalyst for your particular form of expression. I've heard it said that art and music can be a way of rebalancing. Our artistic or musical output will basically depend on what spectrum of our emotional make up lies in the shadow and is hence in need of stimulation and emphasis. Music and art are in this sense a form of therapy.
You might think it's a waste of time considering these things, but I beg to differ. You have to have a reason for making music or doing whatever your form of expression is. If you don't have a reason, you don't have any motivation to do it. If your reason becomes known to you through careful consideration, then you have motivation that comes from within and isn't relying on any external factors such as fame, money, success etc. Furthermore, if you consider the importance of frustration to your reasons and motivation for expressing yourself, you'll embrace this as an essential part of the process. While it's still trying at the time it happens, it will only lead to progress.
Beware of the artist or the musician that constantly proclaims that they are happy or grateful, they are denying themselves or simply ignoring one of the most essential tools to encourage their creativity with.