I suggest you attend graduate school. It was'nt until I completed my Master's that I really understood what I was doing. Even better, if you attend while you are working or after a period of work, you will feel encouraged to work harder at the understanding and no so much the grade. My undergraduate knowledge (for doing FEA) was just pathetic compared to after grad school.
I had done some simple analysis before grad school and I now realize how poor of a job I did. Basically, garbage in = garbage out. To get garbage out in FEA very easy, and the problem is it can be convincing to yourself and others. This is a big problem with analysis today and many of the "press a button and get a pretty picture" codes.