The secret to becoming a good seamstress is...
I know. I hate that fact too. When I was younger, I just wanted to get the project DONE and any mistakes were REALLY BIG STRESSFUL ROADBLOCKS.
Then, when I was in college, I spent a year working in the JC Penneys alterations department. Half of alterations is taking out seams, so I got very, very used to using a seam ripper. I also got used to being a perfectionist, and taking the time I needed to pin and baste things so that they'd sit properly.
I don't like basting. I don't like making muslins. I don't like taking out stitches...
But I don't hate it anymore. These essential steps are just that - essential steps. They are not barriers between you and your glorious creation - they are part of making that creation in it's full potential.
Just as boiling water is a boring but important part of cooking, so is using that seam ripper, and that iron, and trying things on a billion times in sewing.
When I find myself running out of patience, I've learned that rather than sitting there and getting more and more frustrated as I try to solve the problem, I need to walk away. Sew something else, or (more likely) do something else altogether. Calm down. Get my patience back. Think about the problem from a new angle. Come back and see the project with new eyes. Start over again.
Sewing takes time. It's not something you can rush, or it will get messed up. It's an art form. It deserves all the time you can give.