I have ambitious life plans and I'm anxious that they will all fall short.
Why do you worry that that'll happen?
I just think I don't have the skills yet and I should be working harder
It's right to want to succeed at what's important to you.  However, you need to realize that everyone, even the best of us, fail sometimes.  You need to be prepared to fail if you ever want to succeed.
If I fail where's the gain?
We all fail at times and the gain in failing is that it teaches us lessons from the experience and let's us know that we can pick up and keep trying. You shouldn't hold yourself to such a high standards as it is going to make it difficult for you to appreciate your achievements along the way.