Something I read just a while back and made so much sense is to have more than one model on the go at once. If have say three models to work on that will give you a few hours a session to get stuff done. I usually get impatient and rush through the build stuffing things up. If I had another model or two to continue on with I could put each aside until it was ready for the next stage.
^^ that's really good advice. I often rush onto the next coat of paint or what have you...
Similarly, budget and make a timeline for your build. I did this for my last RC car body...
day 1 - rough cut, test fit
day 2 - mask
day 3 - paint
day 4 - more cutting, test fitting
day 5 etc. etc...
I still rushed, but at least I was able to slow down enough to see that I wasn't going to finish the whole project in 1 night.
Shutup and drive yo cah'!