It's all in the mind. Framing is essential. As you've worded it, "[I need to] buckle down and start working" sounds like the beginning a painful trek that anyone would try to avoid. Instead, thinking about the exact same thing as "[I] finally have the chance to play with this interesting problem" will do wonders for self-motivation. As others have mentioned, it's not something that changes overnight, and requires daily practice.
Now, I can already hear the little voices whispering in a few of your heads "that's some optimistic bullshit, lying to yourself, etc." If you've read Self-Discipline in 10 Days, this nagging is said to come from a part of your subconscious dubbed "Hyde." Here's a brief description from the book:
=== BEGIN ===
This Jekyll/Hyde approach is one of the more important
concepts to understand in your attempts to develop self-
discipline. Time and time again, participants in my workshops, seminars, and courses have reaffirmed that this concept, understanding it and applying it, has been instrumental in their self-discipline successes. So, you will begin by learning about how your personal Hyde operates.
Hyde believes:
If I begin a structured, organized journey toward any
chosen goal:
- I'll become a slave to routine
- I'll lose my freedom
- I'll lose my sense of fun
- I'll drown in a sea of responsibilities
- I'll put too much pressure on myself
We all have a rebellious side to our personalities that resists any form of structure. We bring this rebellious seed from our childhood. One of the first words a child learns to say emphatically is "NO." The child we once were still lives inside us, and every child battles authority. Hyde, the name we will call your inner childlike rebel, battles any form of authority, even if the authority is you. Hyde subconsciously says: "Nobody can tell me what to do, not even me."
=== END ===
I find that similar to the framing-work-tasks-as-WoW-quests mentioned above, if I can tell myself that my projects are fun (and it helps if they are, which is why I code as a hobby), I'll be eager to get cracking. That childish Hyde character is still out for a good time, and mine still enjoys solving puzzles if he thinks it'll be fun. A good litmus test is to try and explain what you're doing to a non-techie. If you want to energetically share the details of your project, you're doing something right! If you'd rather not discuss it because it's "boring" or "work"... well, it's obvious where your procrastination stems from.