1. Mabel always bought one lottery ticket in the hopes that one day she would hit the jackpot and never have to work again.
2. I went to the library not expecting to find any of the books that were on my list, but I hit the jackpot. I managed to find all seven of them.

Synonym: hit pay dirt. The expression originates from gambling, in which the jackpot is the money collected from the gamblers and divided among the winners.