Just curious, what kinds of temptations in programming turned out to be really harmful in your projects?  

Like when you really feel the urge to do something and you believe it's going to benefit the project or else you just trick yourself into believing it is, and after a week you realize you haven't solved any real problems but instead created new ones or, in the best case, pleased your inner beast with no visible impact.

Personally, I find it very hard to not refactor bad code. I work with a lot of bad legacy code, and it takes some deep breaths to not touch it when I have no tests to prove my refactoring doesn't break anything. 

Another demon for me in user interface, I can literally spend hours changing UI layout just because I enjoy doing it. Sometimes I tell myself I'm working on usability, but the truth is just I love moving buttons around.

What are your programming demons, and how do you avoid them?

"We will come back to this and fix it later. We just need it working now!"