In his book Strategies of Genius, Robert Dilts quotes a Disney animator as saying there were three Walt Disneys, "The dreamer, the realist and the spoiler. You never knew which was coming to a meeting."
He goes on to say that creativity is a combination of these three elements.
The Dreamer is necessary for creativity in order to form new ideas and goals. The Realist is necessary for creativity as a means to transform ideas into concrete expressions. The Critic is necessary for creativity as a filter and as a stimulus for refinement.
There are a lot of self-help books and experts that tell you the dreamer is the only one you need. That the realist and critic are evil and need to be stopped. Think of how often imagination is extolled as fragile flower to be cherished and never judged. Think of how often people tell you to silence your inner-critic.
Really, isn't it only bad when you try and do all these things at once or get stuck in one without the other two? Personally, I think the critic and realist are one and the same, that the critic just says no to things it doesn't want to work on, but it's a quibble. I think that the model is helpful. In the Disney system Dilts describes, you come up with an idea, decide if it's viable and how it can be done, then you make it better.
Is there one part of this process that you can't do well? Is something holding you back? Try breaking it down into these three steps and seeing what happens.
Dream it, realize it, improve it and then let go of it. It may take years, but it sure sounds simple when you say it like that.