That reminds me of my worst habit as a programmer: I want to solve every problem myself, instead of asking for help.
I certainly don't recommend quitting every time you have a problem you can't solve in half a hour, but there's a happy medium between that and wasting days (while you're getting paid, or at least wasting your project's time) working on something that the guy in the next room could sweep away in ten minutes.
Second that - there's a definite point of diminishing returns and it's worth knowing when you're reaching that point because after that you're just wasting time, burning out, and throwing off future efforts.
When you reach a seemingly impassable problem, talking it over with other people and then sleeping on it will make everything clearer come morning.
If you work constantly you are a worse programmer than those who know to take breaks. These are the people who are thinking about what they're doing.