1) So important to be intentional about your time, and your energy. Start planning your day: http://calnewport.com/blog/2013/12/21/deep-habits-the-import...
2) first and foremost, take this opportunity to find/create more challenging projects for yourself in your current role. additionally, start planning/preparing for how you can move to position with more responsiblity and interesting work -- either within your own group, or elsewhere in the firm, or by seeking a job offer elsewhere.
3) if what you really mean is brain fog or lack of focus, these are the main areas to tackle: - cut all web surfing (this gets back to being intentional about your time, and also resetting your dopamine mechanism -- web surfing is our equivalent of rats pressing hte lever over and over for a treat -- totally useless) - cut sugar - get adequate sleep
4) if you are just not feeling software development (or whatever your current work is), it's possible you want to explore a change of role altogether. i have less to say about that, but worth doing some reflection in the evenings -- perhaps with some pen and paper, or by taking some walks and being alone with your thoughts -- to explore this.
and with that, I should follow my own advice and log off HN. :)