Getting older means realizing how many things you did for the last time ever without knowing it. Thoughts?

Earlier this year I was driving past my former coworkers parents house and saw him (my coworker) having a smoke outside in the front garden. It was over 4 years since I seen him and 4 years since he’d lived there. Now another 6 months has gone by and I wish I had stopped to say hello. I often wonder if that was my final chance without knowing it.