@Line7 I was listening to the radio the other day and heard an interview with The Black Keys guys. I'm not a huge fan of theirs but I do appreciate their musicianship and think they're one of the better bands on the pop scene nowadays. Anyway, they were asked about one of the biggest mistakes they see other bands make when working on recordings (I'm paraphrasing, the exchange was pretty long, they were discussing the other groups they're produced). They answered with saying insecurity is one of the bigger mistakes they see other bands make, ruining their own music and their relationships with other musicians. I'm not going to make the leap and say that's what you're talking about, but to an extent it's something all musicians really need to take into account all the time, and it happens to everyone on some level, no matter how famous or talented they are.
I've started crossing over into trying to help other bands with their songwriting and production, and I'd say this really is the number one mistake. The prized idea, the desire to really do something well and execute it with energy and confidence, this is a feeling that can really effect you, mentally. Sometimes we mix up being relaxed with not caring enough, so the tension builds and more and more pressure starts to push up against our ideas, and the stakes get raised because we feel as though that prized idea is all that matters. Sometimes, especially when things don't seem to be going as they should, or a song just isn't coming together, that insecurity turns quickly to frustration. Only a relaxed mind can deal with this situation, only the security in knowing that you really can do this, it's just going to take some focused and patient work, will get you through the roadblock.
Unfortunately, in my experience, many people just try to bull-rush that roadblock, endlessly trying to play the same things over and over until they tire themselves out. Then they're tired and frustrated, they don't understand what's going wrong because they're blinded by insecurity, and they end up blaming others, or turning it inward and reinforcing the insecure self. Some skills are hard to teach, and nobody thinks of psychology as being an integral part of musicianship (though they should), but it really does behoove us all to approach our creativity with an open and relaxed mind, confident and secure.
So, long post. The point I want to make is this: If you're finding yourself dissatisfied with something creative that you're working on, you need to be able to allow yourself the freedom to change things, sometimes radically. If I was getting bored trying to play a basic bass part, I'd change up those chords, find a new drum beat, mix up the keyboards, whatever it takes to make me more interested. Because let's face it, if your song can't even hold your own attention, how do you think other people will feel about it? Are you going to be able to confidently put that out there and stand behind it, when you know you can't even bear to listen long enough to lay down a few tracks? And most importantly, are you able to drive that idea to completion, or will you draw it out and let it stagnate in your mind, while you hold on to a prized image that will never be realized?
For me, the songs that I'm unable to complete are the ones I know aren't that good. Those go in the trash and I work on the ones I do like.