[flashback:]
Barney: "Sad"? Lady, I got 14 girls' numbers in the last hour. And this was an off night. Heh-heh. What can I possibly be sad about?
The Mother: I think you were in love and you messed it up. And every moment of your life since has been spent trying to stay busy enough to ignore that fact.
Future Ted: [v.o.] And that's how Barney met your mother.