You have three ways ways:

1. Negative visualisation - try to imagine what happens if you completely stop moving and how your body will feel and how bad it will be in one month, year, 10 years.
2. Try to make it a habit - they say that you create a new habit after 21 days. Try to not think about it, noone needs to convince you to take shower or go to work even if your body doesn't really need it. Give yourself a try and put it as constant part of your day. Body gets used to endorphines as to all other drugs so it may work.
3. To give yourself a trial, lets say you will train for 6 weeks, take before and after pictures. If you don't feel better after 6 weeks, you are justified to quit :)

Time will pass anyway, it depends from you how you use it!