I think it is healthy to do this occasionally but if it is more than less, maybe talking to a therapist/counselar may help.
Hiding/withdrawing may be needed for one of the reasons you mentioned, and this is a good emotional survival mechanism.
Maybe it is a good thing too, cause one gets a chance to do hobbies,planting or different things that can bring comfort.
I feel it's alright to vacate from the things or people that are bothering us, it's also good, if you can, get those around you to understand whats going on.
But if it is a form of "me" time, like I call it when I do this is "I'm going into my secret little world" do not disturb. Sometimes I do answer the phone, instead I listen to who is calling and then maybe call back or I have someone who is home,tell them I'll call back.
I need "quiet time", my family,especially my oldest brother respects this and I to him, for he does this occasionally too.
Some mistake it for depression or anger, and get insulted if I do not recieve calls, but once they know why they too, respect my need for space and quiet time.
Take care now,
DE

((((((((( ozzie ))))))))))))