I can relate so much to this topic. I start a project so well, with such focus and drive. Then around halfway, I slow down, start to lose interest, and start getting bored.
One thing I do is do a what I call "limited multi-tasking." I may have five projects that I want/need to do. If I can, I will "nibble" on one project at a time. When I start to get bored, I stop, go to something else and start that.
I may start a big/hard project first, just to make some progress, but save a smaller/easier project later in the day, so that when I do finish that smaller/easier project, I will feel I have done something with my day instead of having 4 half finished projects and nothing really done for that day.
When I have dealt with "fear of failure" in my mind I then ask myself this, "Well, fine if you don't want to finish something because you are afraid of failing, then you have already failed, so can't fear it now." I play this mind game on myself to remind me that fear in this case has nothing to do with safety or such but is an illusion and just my opinion on my own actions. (make sense?)
Also, when I do finish spomething I usually feel anti-climatic and a little depressed, but then I remind myself that if I didn't do it, then no one would. In that case, I reward myself. Sometimes that works, sometimes not.
I hope I helped!
(oh one other thing... this post is a great example of almost not doing something because I felt it was a waste of time and would not help, but I told myself that I can not assume what others would think about this post and that was rude of me.... then I felt who cares if I fail with this post because I was not purposely trying to hurt anyone, but help. I can't be faulted for trying to help someone on a message board)