I think I learned it largely from my parents and grandparents.
They were mostly very patient, so I had some good modelling. I had a grandmother who was almost impossible to annoy, at least as a grandchild.
My mom had me work out some tantrums alone in my room. That got me to see that tantrums tended to be destructive and not very productive and I found for myself something about observing my own state and its impact and choosing to calm down and not choosing the frantic state, and having that work. Tantrums aren’t exactly impatience, but it seems related to me in terms of the choice of calm I am now mindful of and that I use often for patience.
There were also times when I was a kid when I had an excess of energy and excitement and would make lots of noise and run around despite my parents telling me not to, and when they came to stop me either they told me to go cool off in the bathroom, or I fled into the bathroom, and I would cool off in there… which was also sort of about observing my own state (not much to do stuck in a small room with no stimulation) and chilling out.
Also I observed other kids being impatient and noticed how they were annoying to myself and others, and related that to my choice of how to be.
And one of the clearest models I had of patience was airline travel with just my dad and me. He was very relaxed about it, and modeled patience and mentioned his way of relating to it, which is that as long as you do some minimal stuff like show up, check in, and be on the plane, you’re going to get there about the same time, and you may as well relax. Not much actual gain getting ahead of others getting on or off – in fact the experience can be better if you chill and let everyone else get on and off first, and don’t worry about any of it and just find ways to enjoy the time you have nothing you really need to do – reading, puzzles, games, chat, watching people (including the silly people being anxious), etc.
As for car driving patience, being in a couple of accidents also showed me I’d much rather choose to be safe and let maniacs by than be one of the maniacs struggling to get an extra car-length ahead or go 3–6 mph faster.
Basically for me, patience is about watching my own state of being and its impact on me and others, noticing the choices I have and choosing to be calm and indulgent. I don’t always succeed, but some people have marveled at my patience in conversations, driving, etc. I don’t think of it so much as a capacity but as a choice.