past, meet present

This morning I was happily walking to work with MC when I saw a familiar figure ahead of me. It was the significant ex, and he was literally about ten paces away from meeting the current beau. I was completely freaked out about it. I'm not really sure why - the ex is part of another life, and not one I'm particularly keen to revisit. But the thought of two people meeting with one thing in common - me - makes my toes curl. So I slowed down, and took an early turning into work, and watched gratefully as he receded into the distance. I didn't tell MC because I couldn't even explain it myself. I've met the ex's girlfriend and been fine with it so really, there shouldn't be an issue. But somehow, there just is.