I rarely have moments when I have nothing to do. But sometimes it still happens. I'm trying to do what is beneficial to themselves, such as cleaning the house. You can clean up on your desktop or make simple rearrangement of furniture or clean the floor. Nice clean feeling to himself, moreover, is "kill" time of 15-20 min. You can still do sports. Pushups, squats, press. So the time will be for the benefit of your health and your body. Another option, spending time to go for a walk. This is a great way to relax. And, you can call your other half, wondering how things were going well .... fly quietly for 20 minutes. Another good option is to read an interesting book, develop your brain, too, is helpful. You must use the time usefully, life is given only once. And spend it on stupid idleness.