A BDSM relationship is like any other relationship with all the ups and downs and various complexities you'd have in vanilla relations. Maybe evenmore so since it demands greater honesty with your partner and yourself as well as deeper intimacy as a result of that mutual honesty. That is why the moments after the chains and whips and nipple-clamps are just as important if not more so than the fun and scary and arousing stuff people only ever think about when they think of the lifestyle.