If you take a job, do your best work possible. One of the bad things about lowballing jobs is it creates an atmosphere of doing things just good enough. I make sure that if I agree to a price for a job I get paid well enough to do my best work. If you aren’t going to do your best don’t take the work at all.
Reward yourself for a job well done. One of the things I learned was to pay myself first. Give myself a little treat when I finished a job just to make the parts of it that weren’t fun worthwhile. In really slow times that might not be buying something, it may be just a day off to sit around and read. Rewarding yourself for a job well done is important, especially as a contractor when a lot of the time the only compliment is the check.