Dear friends, I don't know if it makes much sense to write about this but see if you can help me. I'm a second year undergraduate and I've been working a lot on Mechanics and waves. It's the subject I like the most but unfortunately I failed both exams we've taken so far. It's the first time in my life that this happens to me, so although it is not so important, yet I feel a bit shocked and I take it as an intelectual failure. I did thousands of problems and I think I understand the fundaments of Lagrangian mechanics, rigid solid, central forces etc. But it seems that I doubt of everything I write down on the examination. If I failed my favourite subject, how can I pass others such as Thermodynamics? Thanks for your words.