hi, im joaquin from buenos aires, i think your comunity is very usefull! and i want to give my point of view
about the spirit training, i can say that it envolves every aspect in Parkour. David Belle once said, that if someone trains one day with his father, probably he/she will no longer want to do the training again. He said that if you really train parkour you will bleed, you will cry, and you'll be exahust. If you want to "go easy", then parkour isn't for you.
when i started training, for example, my progressive training was slow. But parkour made me go beyond my limits.
Parkour gets you really motivated because you know WHY you are training. IT's not like doing fitness in the gym, probably you dont' know how it can be useful for you.
But here you know that, you want to break down every mental and phisycall block.
Like chippa said with running, sometimes you think you've got to stop, your legs want to stop and you are breathless, but if you try harder, you can go on.
The same with push-ups or any excersice...or balance even, sometimes it's just a mental thing and you only need to convince yourself that YOU CAN GO ON.
thas what i think, sory if my english isn't perfect! hope you understand me.