This is hard for people who live in the city or far from any beautiful green spaces but if you're anywhere near the Yorkshire Dales, it's really easy. A micro-adventure is anything that feels good for you. You don't have to rock climb - you might just skip dinner in front of the TV in favour of an impromptu picnic sitting on a Dales rock admiring the view. Or perhaps you could dash out in your lunch break or before work to do a little wild swimming, or maybe just some paddling or mud-larking? The idea is to simply feel like you're living, not just existing.
Micro-adventures are brilliant with children - and sometimes it's the simple things that work best. A long time ago when my daughter was young, we had a storm with masses of thunder and raining. I think she was a bit scared and to distract her I came up with the 'genius' idea of both of us taking off all our clothes and dancing naked in the rain in the garden (it's quite a private garden!). Fun, free, easy entertainment that we both still look on fondly. Another time I took a friend's children to the top of a Dales hill. They were city dwellers so not used to climbing uneven hills, and their walks at home usually ended with an ice cream or other treat/bribe to get them out of the house. I promised them a slightly different one - the chance to do something their mother would never let them do at home. When we got to the top of the hill, with no one in sight/ear-shot, I challenged them to scream and shout as much as they could for as long as they could. I still remember the joy on their faces when they experienced such simple freedom.
Alastair's Do Lectures talk is great - watch it below and go to his website to see more about how he's made a life and a living out of having fun.