The first way I have begun practicing is creating a list of each goal I want to accomplish for the week. The important part, for me at least, is making sure this list is as specific as possible while not being too ambitious. Ensuring that your list is easily achievable for the week will help manage any stress and anxiety you might have about completing it. So far this has been the most motivating way for me to get things done.
The second step I've started is creating more deadlines. Even for projects that may not be very high priority. If you have a goal you want to complete, but its not imperative that it must be done within the same week as the rest of your list, add it anyway and give it a deadline. This is an ever shrinking reminder that you want to get this done. Keeping track of your progress on more important goals will help you find the time to fit in those lesser ones somewhere.
Third is have an accountabilibuddy. Talk about your goals, and pick a time to go over them with someone each week. It is a lot harder to put off something when you know somebody else will be checking your work. You not only want to prove to yourself that you can get your work done, but its rewarding to show someone else as well. This person may also have valuable suggestions on how you might better manage your workload, as having an outside perspective is always important with any kind of creative endeavour.
What about that inevitable monkey wrench? You know the one, it always comes sooner or later. Allow me to regale you with an anecdote from my very recent personal life. You may or may not know that I am currently going through programming classes, while simultaneously working on my own indie game, applying for internships, and also trying to find time for animation practice. There are a lot of goals I could potentially fit into one week with that kind of life, and for the most part I had that goal list set reasonably. That is until finals week started. Always sneaks up on me sooner than I realize. Suddenly my schooling, which already took a good 40-50% of my allocated goal time, has been turned up to 11 as I finish the final 2 weeks of classes. This has made it pretty easy to fall behind on the rest of my goals.
So what do I do in this situation? I'm still figuring that out for myself, but I can tell you that each step I listed is like a failsafe for the previous one. If my list was too ambitious for that week, I'll push back the tasks I didn't get done and add a deadline for when I WILL get it done. Having someone to talk to about it, whether that's for helping find a new way to manage those expectations, or just to help keep me from beating myself up over it, is a huge help. The final piece of advice I can give, and one that I've struggled with all my life, is don't be afraid to ask for help when you need it. I can't pretend I know what is best for you. I barely know what is best for myself. So in the end let me ask you for help now. Let me know that kind of techniques you use to stay on task and keep yourself motivated. Every perspective is worth hearing, and there is always more to learn!