I second get a hobby or take a class. Relish in the help and the break. I was a single parent for 15 years and it's tough. It's all you all the time. I love being a mom but I single mom is the hardest job in the world.
If you take classes in something you are interested in or looking to advance your career by obtaining your MBA or undergraduate degree. This time minus the kids will be priceless. The time does go by quickly though and before you know it they will be off and out of your home and then you will have to once again figure out life without them.
Children are not really supposed to be our lives but a part of our lives. My son, neices and nephews I have raised all know I have always had a life with or without them.
You may even consider learning to play an instrument. 1,000 hours consistently at doing something will make you an expert at that thing. Make the time without your kids work for you. Also consider there is nothing wrong with using that time to tighten up the house with some major cleaning or perhaps redecorating the place.
What ever you do. Make it fun for you.