[chuckus]

Totally agree, I've got a solid applied calculus background from my electrical engineering undergrad degree and some DSP in my first job, but avoided learning statistics and probability because I thought it was intuitive. But after doing a MOOC course on Machine Learning, I realise that statistics and probability is more complex than anticipated.

If you don't work on your fundamentals, you end up simply memorising the algorithms and basic applications. Much like the neurons discussed for deep learning, we need to create rich relationships between our own to ensure we retain and can apply the knowledge in the long term, which starts with laying a foundation of fundamentals.

For brushing up on those fundamentals, I recommend Bertsekas & Tsitsiklis : Introduction to Probability. Theory supported with lots of examples, as well as comparing the theory to "intuition" and why it is much more effective to apply the theory.