Years ago. There was a teacher I hadn't got on well with at school, I had probably been a bit of a bitch (low level disruption, arrogance, generally being a bratty 14 year old). Anyway I couldn't find my name on the list for exam room before one of my GCSEs and managed to get myself into a state. She calmed me down and was really nice to me while dispatching another teacher to sort out the missing name situation. I didn't deserve her kindness.
I fell off my bike recently and lots of strangers stopped to help, got me up, righted my bike etc lots of people all very nice to me.
I had too many food shopping bags and a strapped up wrist on the train the other day. I couldn't scoop them all up. A man lent over and gathered them up for me.
I have a large musical instrument. The amount of people who offer to help on the tube is amazing. I don't need any help with it (my choice to play it!) but always thank them and joke that I'm well practiced now.
When I was little I fell and cut my face open, LOADS of blood. We were quite far from the car. Some strangers stopped, helped keep the cut together with some plasters they had in there car and have us a lift back to our car. That was nice.
In terms of paying it forward, I try to be nice and generally a bit helpful, very small things mainly. One bigger thing recently which was quite alt after people helped me when i came off my bike. A lady fell of her bike outside my flat. People outside got her and her bike out the road and stayed with her for a little bit. I was watching out the window. Then people kinda drifted away.
After about 5 mins I decided she really didn't look like she was ok - went out and she kept saying she was fine, no ambulance, she was fine. But she wasn't moving from her sitting position and was very white. I called an ambulance, sat with her quietly letting her know one was on its way.
I took her bike into the flat for her as she didn't have a bike lock with her and the ambulance wouldn't take it too (obviously). She wasn't ok, had hit her head and dislocated her shoulder. Couldn't believe how quickly the ambulance got there to be honest.