As much as I hate to add another vulgarity to the database in the form of a node title, this is probably necessary for completeness of Southern slang. I've heard this since I was able to understand anything an adult said. We grew cotton on the farm where I grew up, but I don't think I was the only one who ever heard this phrase. It's pretty self-explanatory, I suppose (even though no one ever actually sat down and explained it to me).
When you have to relieve yourself outdoors, nothing makes better toilet paper than a few cotton bolls. And, if you're in high cotton (good cotton can grow as tall as 4 feet), you're in a good spot to reach over and pull off a couple.
Agricultural alternatives which aren't so good? Corn cobs. . . . Ouch.
The implied meaning is that things are going well for you, or that you have joined a group of elite folks.