If you just think you will probably die tomorrow it won't really work because secretly you don't believe that. It didn't work for me until I was talking to myself the moment is _all_ my life. If it's not all your life you'll feel fine wasting it because you always have more.

As for external motivations, I guess everyone is different. I sweat on external pressures and I avoid doing them at the last moment then I procrastinate because I feel worse and worse missing the deadline. I guess everyone works differently :)