Decide, commit, don't make excuses.
Sometimes you'll have to take time off... maybe you're just exhausted because of something special happening, or going on vacation with family, or sick. Stuff happens, and that's ok.
To me, there are a lot of similarities with making games and doing exercise. Lots of people say that want to exercise or make games. Very few actually commit and stick with it. Starting is easy, finishing is a skill.
One word - "evolve". Here's my scenario: I started creating a game maker for me to make games. I use it to create games and play them. Now I'm porting to C++ so that I can create my own embedded Raspberry PI console. Short thing to take away from this is that you must also use your software or find people to play your games otherwise it loses value. Don't wait to finish the project - get some testers or play it yourself. This will give more motivation in development.
If you don't want to finish it, don't. Finishing things gives you the reward of being able to say, "I finished it." This may be useful if you are trying to put together a portfolio, but if you are bored with the project then you have to consider how much value that is compared to freeing your mind to work on something else. If I am bored with a project, then I consider "I finished it" to be +10 but "I am so fricking bored forcing myself to work on this when I want to do something else" to be -20 or less.
No need to do something you don't want to do just because people artificially weighed the value of a completed project as higher than it really is.
But if you want to avoid this in the future, pick projects that not only are very interesting to you, but that can give you a feeling of completeness before it is ever actually complete. Pick projects that give you rewards at many points during their development cycles.
For example, I am the author of MHS (Memory Hacking Software), the primary competitor for CheatEngine. While working on it, I advertised about it on the typical cheat sites and gathered a following and put up forums so that people could talk about it, discuss improvements, etc.
Now with a community based around it, each new release was its own reward for me. For each new feature I added, I got to watch the community reaction, which motivated me to keep working on the next new feature, and the cycle repeats.
The ability to watch the community use my tool and keep up a cycle of interactivity with them fueled me for over 7 years on that one project.
Pick a project that rewards you in steps along the way. If all you are doing is working in a black box with no reward until it is all finished, it is really hard to stay motivated.
L. Spiro
