Clean up your code before you leave for the weekend

Yes, very important. Otherwise, you return to work and find your program behaving in a really weird way, requiring you to spend some time to figure out why. Especially, when you just wanted to try something quickly on Friday and then on Monday forgot why and more important that you put

for (int i = 0; i < 1250; i++){
...
}

somewhere in your code. Took me about 20 minutes to find that loop and another 10 to remember why I put 1250... damn it ;)