There is a bridge that at some point every artist must cross. On one side of the bridge lies tentative brushstrokes, muddy paint, overmodeling, and lack of confidence. On the other side waits purposeful brushstrokes, mastery of materials, clear concepts, and a solid belief that you are on the right track. How do you get from one side to the other? That's the big question.
One factor that you can't control is that it will take time. You have to pay your dues if you want to sing the blues. You have to give yourself time to learn your craft and evolve. There are, however, things that you can do to help the process along and make sure that you don't end up spinning your wheels in one place, not moving. Preparation is a key element to painting with confidence. Do your homework. Read everything that you can get your hands on. Know your business. Very often when I'm taking a class I'm amazed at how uninformed and unprepared some of the students are. If the instructor has to take time just to get you to point A, how will you ever get to point D?
Usually when I'm floundering around, tap-tap-tapping my brushstrokes, completely in panic mode, it's because I haven't done all the preliminary work that I needed to do in order to successfully paint. Some artist's have the idea that painting should be improvisational, like jazz music. What they may not be considering is the thousands of hours those musicians spend practicing scales and technique. When I was first learning to paint, my instructor, Robert Armetta, told me that I should do a lot of small, single session paintings. They are a good way to develop confidence in paint manipulation and all the problem solving is done on the spot. You don't let the painting go until it's truly "done". I did a lot of these. I put the paint on thick and I tried to use just enough brushstrokes to create form. It's kind of like painting a small still life with a landscape sketch mentality; get it down quick before the light changes.
You have to learn to trust your own instincts. There are a lot of artists out there who are absolutely certain that there is only one right way to paint, theirs! Try to deconstruct what ever method you are using into stages. Analyze each step and determine what's working and what needs improvement. My achilles heel is drawing. I've always been good with brush and paint but I realized those skills weren't worth much if the drawing didn't hold up. So I went and got the training that I needed and that has in turn helped my painting.
Try not to go into panic mode while you're painting. It's normal to have doubts, but also understand that the mind can play tricks, so if you have a plan, stick with it. Later, after you have put down your brush, you can reflect on different choices you might have made, and use those lessons to do better on the next one.
If you are serious about making art than you must have something you want to impart to the viewer. Technique is just a means to an end. You don't want your "message" to be short-circuited by being overly pre-occupied with the craft aspect.Get your craft to the point where you're not thinking about it while you're painting. You're doing what you do. If technique is important to you, that will come through in the manner in which you put forth your ideas. I prepare for most of my paintings with thumbnail sketches, color studies, a full scale drawing, underpainting and a pre-mixed palette. That's what gives me the confidence to proceed. Find what works for you and stick with it. Add slow refinements. Jumping around too much leaves you no place to start from. It is my belief that anyone can learn to be a competent painter. It's not really that complicated. To be a great artist is a different story. That has more to do with what's inside your head. Forget the tortured genius cliche. The great artists of the past all painted with the confidence that can only come from arduos study and long hours at the easel.