One time my wife and I were out for a ride (a rare enough thing right there), she I the lead. We passed a guy who was futzing with his bike. I stopped to see if he needed help. And he did; really did. He had a flat and no pump/patch kit. My wife still hadn't stopped and was already a quarter mile away. I realized this guy was going to use up fifteen minutes of my time and ruin my wife's ride. This was before the days of cell phones, fwiw. If I didn't catch up with my wife soon, she'd pass a intersection and I wouldn't know which way she went. "Sorry, man!" sez I, and left him in the lurch.

Sometimes you just can't.