I think actually will be good! If this is really important you will find to spend some time visualizing and taking care of yourself. I think being busy might also take away from spending time thinking negatively. Also being busy means you are doing your life which is what you are supposed to do. You don't have to necessarily set out a specific time to visualize. you can but I have found I can visualize while doing other things and that works. Those times I find its a bit more like daydreaming but it still works just as well. With your busy schedule I am sure you will find a way to add this challenge into your routine. It's not about the time you put in. It's more about the energy you put in.