If you've eaten your fill at a big meal, you know by your full stomach that you have had plenty. In fact, if you had more than plenty, you might even get the feeling you've had too much!
The word plenty usually refers to more than just enough, and this comes, via Middle French plenté, from the Latin word plēnitās, "fullness," from plenus, "full, complete." The meaning is apparent in the following quote by English novelist George Eliot: "I think I should have no other mortal wants, if I could always have plenty of music." May you have plenty of what you need, and some of what you want as well.