A few days ago, a PhD student asked me if it was OK to take time off during a PhD (specifically to spend time with family over Christmas). There are many reasons why I think it's necessary to take time off sometimes, but perhaps the most important is what it says about how you treat yourself...
Imagine, for a moment, that you're not a PhD student but a manager trying to get the most out of your workers. Would you tell them;
- to never take a day off and to work every hour available?
- that work comes first and family second, always?
- to work to exhaustion, no matter what?
Hopefully, you answered "no" to all of the above. You're unlikely to have motivated and productive workers if you treat them this way. But If you wouldn't say these things to someone working for you, why would you say them to yourself?
As a PhD student, you are effectively your own boss. Your supervisor may (or may not) give you some direction, but it's up to you to decide how you manage yourself and the work.
So be a kinder boss to yourself; give yourself permission to take some time off when you need to, let yourself rest and relax and spend time with the family. The PhD is important, but those other things are important, too.