* Figure out how to write AI for games. A simple example would be, how to write a bot that finds shortest path out of labyrinth.
* Check out graphics programming
* Try to see if low-level programming is for you: kernel level, GPU, OS
* Check out infosec industry, there should be a lot of fun there: malware analysis, penetration testing, etc
* Machine Learning: tons of coolest stuff. predicting, classifying, reinforcement learning, neural networks. Check out Kaggle machine learning competitions.
* Checkout competitive programming sites. My personal favorite is hackerrank.com, but other popular ones are topcoder.com, codechef.com, codeforces.com. Try doing challenges for a couple of weeks you may find that you learnt as much as you previously learned in a year. Also through it you may get interested in particular algorithms and fields.
* Distributed programming, system engineering. How to build systems at scale? How to process tons of data in parallel.
If you don't seek for the new challenging things to do that could improve you, then you will find boredom and burn out in any field.