Missed Opportunities

It's been said that when opportunity knocks, you have to be willing to let it in.  What happens when you are trying to get to the door and something blocks your path?  One of my old managers from a previous job was in the area today.  We were supposed to meet up for drinks and to catch up on old times.  My work schedule prevented this from happening.  I missed the opportunity to see an old friend.  What do you do when something prevents you from seizing an opportunity.  You adjust and seize the next one.