So, I finished my undergrad with a degree in *applied mathematics*, but when reading some graduate level texts and/or papers, I often find myself struggling. I eventually get there, but I often feel like I lack the intuition necessary to be able to come up with concepts on my own. I feel like I'm just missing some pivotal step in the journey to mathematical maturity.

Does anyone have any books/references/advice? 

PS:
If this means anything at all, as I was not a *mathematics* major, I did not take analysis or abstract algebra.