I have been finding it hard to go to the gym after work for a few reasons: there's a lot of things to take care of at the house, I'm tired or I'm hungry. But recently, I have been convincing myself to go to the gym... even if it's to do 15 or 20 minutes. After the workout, I feel better and tell myself that 15 minutes is better than no minutes. So when you say you don't have time, your tired, or whatever the (excuse) reason my be, just go for a short period of time. There is always time for 15 minutes. Once your there, you'll probably stay a little longer too.