Once it becomes a hobby and enjoy it, you will become dedicated to it. You'd find that things like discipline and consistency falls into place naturally.
Mental burn out might not even happen with sustained high volumes. At least for me there is no off-season, i just continue to train. No issue at all......even with crazy hours.
The only issue i am slightly worried about is injuries, but seems not to happen with me.
Another thing i am keeping a tab on is "addiction", which leads to overtraining and unhealthy habits.