Let us pretend you are walking down the street. There is a wind. You look down, and see a $100 bill being tossed along in the wind and land at your feet. Look at this lovely thing that has just blown your way. Completely by chance, the possbility to get some money happened.
Now, apply this as a metaphor. There is no street, no real wind, and no actual bill. But still, by chance, some good possiblity came your way.