The thing is, saying no to requests from management (if it is your management of course) is going to hurt your career prospects too. Instead you should say "sure, but this thing will move the completion date of this hard and extremely important project X days, is it ok with you?" (Not having any hard and important project in the works? Fix that ASAP as the article suggests). Then ideally you reach some kind of compromise (sometimes these requests are urgent and you are the best person to handle them). If instead they say "no, I want you to do this urgent thing and complete your other projects on time, here is a nice weekend that you can use", then it is time to look for a new job.