That discipline is why I thought it would help my depression giving a structure to my life I lacked.
I can't say from a traditional Christian belief, more from a yogic tradition. So, discipline is the key - you get on your mat every day. It doesn't matter if you feel like shit warmed up, because you were drinking the night before, you have a bit of a cold coming, or you're tired, you unroll your mat. If its only for ten minutes, that's enough, it doesn't have to be a full 90 minutes of vigorous back bending, and turning yourself inside out.
All these things are life time practices, faith dips and lifts all the time, not every practice or prayer is intensely devotional, or answered in the way you want, or even at all.
All the people that I know, in the esoteric arts, or religious faiths, where they have totally given up after really trying, is where the practice has not been integrated into their life - this is usually combined with the teacher/ leader being put on a pedestal, so faith in the practice or teachings are not being grounded in the individual.
I don't think its the fault of the individual. There's a lot of crap teachers out there, who are only a step ahead of the student, convinced of their own spiritual gift, or just what to make a bit of cash out of it. Equally, if people just want to go to church at Easter and Christmas and the odd Sunday, or just want to go to a yoga class once a month when they fancy it, that's fine. It's not for everyone, but if you want that kind of depth of faith and sense of solidity in your practice, quite honestly, its just bloody hard work.