Unless I'm mistaken, a MUP is a multi-use path. That means pedestrians, roller bladers, dogs on long leashes, young children wandering about, and bicycles too. You have to be very careful biking on a MUP because at certain times, it's practically an obstacle course. I think you had a reminder of that today. No sense in beating yourself up more about it. Learn from this incident and move on. Next time you're on a MUP, remember that it's not a bike-only lane, and as a cyclist, you're going faster than almost everyone else using that path.