Switching off is the hard part.  My advice is to find a hobby that you can lose yourself in. If reading is your thing get your book and drive to a park for half an hour or so;  take a coffee or a cold drink and a snack with you.

i have a purpose built sewing studio and my husband doesn't enter it without permission. I can walk in, close the door and the curtain and he leaves me be. It sometimes takes quite a while to switch off. Other times i switch off as soon as i pick up a ruler or rotary cutter.

I won't try and kid you that it's easy. It's not. But like anything worth learning it gets easier with practice.