When do I stop doubting myself? I'm a third year Mechanical Engineering major. I'm constantly doubting myself recently. I haven't been able to focus myself in my classes either because of it. I feel like a failure. I'm getting A's/B's in Circuits, Diff Eq, Statics, and my Tech Writing course. But I'm doing terrible in thermo and it's bringing me down. Because of that I am doubting myself in my other courses and I constantly feel that because of the one class I am going to fail out. How can I stop doubting myself? How can I start studying and feeling confident again? Advice/Stories are welcome.