Follow what your heart and bodymind are telling you, not what you think you "should" be doing. It sounds to me like you "want" to train for that long because you feel like you should. Training for that much is certainly admirable and impressive, but it's not always the best way. Everyone is different and believe it or not, even when you aren't actively training, you are still "training" in a way. The bodymind is constantly working in the background, repairing cells, working out pathways, figuring coordination puzzles, etc. This is not an excuse to sit on your couch all day, eating potato chips ("No, really, I'm training! You just can't see it!") but it is a nice thing to keep in mind, to keep yourself from trying to force yourself into a training schedule that isn't a fit with who you are.
It may sound overly simple, but it's true: if you really want to train, make yourself train. If you really want to stop, stop. Only you can make that choice: but make the choice, accept it, and live with it. There is no value judgment on it except what you yourself place on it.
Ultimately, like Charles said, you have to train for reasons that come from inside you, and only you. If a day comes where you feel like you "should" train, but you tire out, or find reasons not to, then you need to sit down with that feeling and examine it. Is it accurate? Are you genuinely tired? If so, then rest! If not, then push through. But either way your choice should come from inside you and your own reasons, not what you feel like you "should" do. Your bodymind naturally has a way of making a priority out of things that are most important to you. One person's training schedule is not the same for everyone. Find other ways to make parkour fit into your life if physically going out and training isn't practical for you for whatever reason on a particular day.
There is a fine line between setting a schedule and sticking to it/showing dedication, and naturally following what's right for you personally. We would all love to work on a superhuman training schedule, but that's not realistic for most of us. So the trick is to find a level that works for you--that is challenging and makes you grow as a traceur, but that is realistic enough with who you are and your lifestyle that you can stick to it and feel satisfied with yourself.
I guess the upshot is, stop "shoulding" on yourself!

Hope that helps. Good luck!