I got better about this when I started making my projects much, much, much smaller. Like ridiculously small. Instead of cleaning out a closet, I clean one shelf. I don't clean a whole drawer, just half.
My whole house needs paint. I have been slowly woking through one room at a time by only focusing on what I can get done in 15 minutes. I wrap all of my brushes and rollers in plastic wrap, so it is easy to unwrap and do 15 minutes of painting. I do my 15 minutes and then decide if I can do another 15 minutes. Sometimes I can, sometimes I rewrap the roller, put the lid on the paint and wash my hands. Done!
I am much better at the 15 minute method than trying to find a whole day to get a big project done. I just get too tired, too distracted by 'Mommy, Mommy, Mommy" or simply bogged down by a big job. The painting has gone quickly with this method, because I use those little chunks of time that would normally go unused. I use a baby gate to block off the room I am working in. Last night, I painted a whole wall of dd's bedroom while my littlest one was in the bathtub. One wall done, three to go.
All of those little projects are just that...Little. They take no time at all, but somehow get built up into giant projects in my mind. I sit and stare at the light switch cover that needs to be replaced. I have had the replacement for months, but never get around to it! Ridiculous. What is it?!? Three screws. It is a 2 minute project. It will take me longer to walk to the work table and get a screw diver than it will to actually do the job.
Another big help is that I built myself a tool/work table in the basement. It is the best thing I have done for myself in ages!!!! I love it. I keep all of my tools there, all of the paint and brushes and drop clothes. I am ridiculously neat and organized about my tools. I want to be able to grab a tool, do the quick job, put the tool back, and be done!
I also keep a list. A huge long list! It is broken up into small, medium and all day jobs. Dh and I try to do one thing a day. We are in the process of selling our house, so there is tons to do. When we have a moment of down time, we have a pact...do a job first, then flop on the sofa. The list keeps getting shorter and shorter and we are actually getting things done.