There's no more relaxing thing to do on a weekend when you feel like a pick-me-up (other than shopping hehe) than to turn your phone off and enjoy the sun, the air and the open landscape extending further than your laptop screen.
As a suggestion for a day out of London, I recommend Thursley Nature Reserve, a mix in between marshland, open fields and a sort of plank-walkway that reminded me of Scandinavian beaches.