Hey Kelly.
This is a great question! I think you'll be happy to know that with the one park per day ticket, you can leave and reenter the same parks as many times as you'd like. I actually do this all of the time. My typical Disney day often starts very early in the morning. I love to be at the Walt Disney World Theme Parks before they open. From park opening until about 11:00 a.m. I find that I can experience a number of attractions without very much waiting. Around lunchtime, I like to head back to whichever Walt Disney World Resort Hotel that I am staying at for a dip in the pool. After swimming, I like to get cleaned up and have a nice sit-down dinner somewhere. Some of my favorite spots are
'Ohana at Disney's Polynesian Village Resort,
Cape May Cafe at Disney's Beach Club Resort and
STK Orlando at Disney Springs. After dinner, I head back to the parks for fireworks and to experience more attractions with low wait times. It's a great way to spend the day! If going back to your resort for a swim doesn't interest you, there are still so many fun things you can do once you leave the parks. Another thing that I enjoy, especially when I am at Magic Kingdom Park, is hopping on the monorail and visiting one of the resorts that it services. A break at one of the resorts for some snacks and maybe a drink at one of the many lounges is a great reprieve from the Florida heat.
Tambu Lounge, also at Disney's Polynesian Village Resort, is a great relaxing spot for this.
I hope this helps. If you have any other questions, please feel free to come back and ask.