The breakthrough for myself as a programmer came from intro CS classes....it may seem odd but I would still recommend going back to the core CS topics of data s

The breakthrough for myself as a programmer came from intro CS classes....it may seem odd but I would still recommend going back to the core CS topics of data structures and algorithms, focusing on the implementation - on what kinds of language features might be used to implement these things, and how the language interacts with the hardware. Just pick a promising field of study - encryption, text processing, compression, search, whatever. Choose a common and well-understood algorithm in that field, do all the research you can, implement it, and then try writing something around it. The key for me was to have some code of a non-trivial complexity to play with. This would be something that you would be willing to rewrite four or five times and really master. Having an interesting application in mind helps one get there, but one can often flip states between "interesting app" and "interesting problem" in programming. It's not in vogue nowadays, but Knuth's Art of Computer Programming is chock-full of this kind of "programming exercise" and it makes a pretty good reference too.