Though I wish I had the luxury of working from home, alas, I do not. I'm an IT technician in a boarding school, working varying hours approximately between 7 am and 4:30.
During term-time, when things are more hectic, I get one break aside from lunch at about 10 o'clock, in which I escape to the staff room for a piece of fruit or a biscuit and a cup of tea. I think this break is really effective because I can talk to members of staff outside my department. It's nice chatting with the Psychology teachers or the PE staff about the news or weekend plans. However, if they start asking me to fix their problems whilst I'm clearly not working (as some staff members are known to do), then I'll hide away in one of the other, lesser-popular break rooms with a book (my current read is Neil Gaiman's Neverwhere, which I'm thoroughly enjoying and would recommend). These breaks are about 20 minutes.
Outside of term-time, things are luckily more relaxed. The whole team takes their break together in these instances, again in the lesser-known Housekeeping break room. Cup of tea. Biscuit. Nonsense nattering about holidays and TV from last night. These vary from 20 to 30 minutes, once at 10am and again at 3pm.
In either case, I think getting away from a screen is crucial. Real, human interaction or peaceful quiet time is equally important - simply whichever tickles your fancy more.
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