Sometimes I feel like I don't improve as a developer. I'm referring to the net amount of information that must be flowing into my head on any given day just to keep up with it all. As soon as I focus on, say, upgrading my CSS skills, I lose track of new developments in, say, jQuery, or any of dozens of other things I need to stay on top of. I don't improve. I just stay afloat.

stack, you're stuck!

Have a clear timetable and be disciplined enough to stick with it till the end.
Some techniques i use:
-Wake up one hour earlier than normal and learn something in that hour.Make it a habit that each day you study the same thing in the same hour.If today you started with jQuery,then each morning hour is jQuery hour.
-In your side projects,don't use the normal tools you usually at work(preferably use a tool you want to master).
-Be disciplined in your online classes. Always strive to meet the assignment deadlines and NEVER copy solutions.Remember some of these courses are free and no one will punish you if you did it wrong,so it doesn't hurt to make mistakes.
-Learn the same material from different sources.It's important to have different interpretations of the same principle (especially Machine Learning)
-Be repetitive in learning things.(Always come back to a concept after some time so that you don't forget it)