English Portuguese (Brazil)
First and foremost, though, don't just vanish. When a contributor or potential contributor agrees to do work, can't follow through for a valid reason, and vanishes, the team may not know the work can be reassigned. In some cases, people in the team may even worry about the contributor's health or well being.
When you've decided it's time for you to go or take a break, let your sponsor or the list know and let them know what you were working on. Having people think you are working on something when you aren't slows the team down, and ultimately doesn't benefit you or the team.