Since I am married to my wonderful Wife/Mistress, I may be answering this from a different perspective, but by the same token I can refer back to my previous D/s relationships as well.

My Wife & I are great believers in increasing, uplifting, & sustaining each other's self esteem. She is very loving & caring, in addition to being very exacting & strict, but to us, the loving & caring go hand in hand with the exacting & strict, so there is no differenciation in the mix.

The closest we get to "pulling down" my self esteem is in the few times that we do a bit of mild humiliation play, & that is different & is treated as such. Even mild humiliation, (not in play, but in reality), can actually bolster one's self esteem however. An example is when a sub needs to be corrected/punished, (for those into this aspect of D/s), for failing to please their dominant. The very act of being punished has it's own shades of humiliation, & humbles one before the dominant, thereby reinforcing the lesson being learned by the punishment. Now once you learn a lesson, your self esteem increases, doesn't it?