A psychologist told me the key to making sure you do something regularly is making it part of your identity. When you do something for a time, and then suddenly drop it, chances are you never incorporated it into who you think you are.
I don't wantto get into the affirmation game — because who needs that — but it's like looking yourself in the mirror and shouting "I struggle with my money management!" instead of, "I manage my money."
The former anti-affirmation reinforces the self-image that you can't keep your finances straight. The latter may be a lie at this point — but if your goal is eventually become fiscally responsible, then you need to start believing that you are.
What do you want to do? If you want to make sure you write everyday, then you need to see yourself as someone who writes everyday. Instead of thinking, "I will try to write for one hour every day." Think, "I am a person who writes every day." Better yet, why not do the mirror thing? Stand up, look yourself in the eye, and declare it! We won't tell anyone ... maybe.
The more you think of yourself as a dedicated writer, artist, or whatever it is you want to be, the less likely you'll be to drop off. So ask yourself, "Just who do you think you are?!"