I like working and dont think I could ever retire and relax type deal. But I also tend to overwork myself by always taking on more and eventually get stressed and 'need' a holiday which has 2 positive effects;

1) Some downtime is good, see somewhere different and hang with family/friends etc

2) After a bit I get bored doing holiday activities and remember how much I like to work. I think this is actually the most positive benefit of a holiday.