When I get down on myself, it's almost always because I feel like I should be able to do everything--all the time. I look back on the day and see what I've done, and get crazy because there are 30 other things that I wanted to get done as well, but couldn't fit.
I have been getting better about this. I've rearranged my "to-do" list and now structure it like this.
Morning: Pick 2 things which are vital and for "Immediate Action" and get them done before 11 a.m. Sometimes these take more time, sometimes less, but this is the primary goal and if these things get done, I try not to get stressed about the other stuff.
I divided the other tasks into 4 categories: Photography, Painting, Home, and Business. I then try to make sure that I spend an hour or so on each category, then move on to the next, so that each day I'm able to touch on at least some of the things from each category that need to be done before the kids get home and things become more chaotic and unplannable. (is that a new word?)
It's tough when things take a long time and I have to decide whether to ignore the other categories or not, but I try not to. I also try to limit things like checking email and the internet, leaving my home studio (because things always take 3 times longer once you step out the door than you think they will).
One thing that I say to my students is that "Continual Improvement Equals Success". In my situation, I suppose this is should be "Continual Forward Progress Equals Success".