One of the things I have noticed that many people do with BDSM is get into it to a point where it is all they focus on. Their relationship centers solely around BDSM. Any discussions take in only BDSM related topics. This kind of overkill, though understandable, can and will eventually wear off. Leaving those involved feeling as they have "lost" their world. Or lost their feelings for BDSM. This can lead to very damaging beliefs that they are not what they thought they were (iE; dominant or submissive). This period of time can become a major problem and break a relationship that is otherwise perfectly fine. 

When one thinks of vanilla relationships, they thinking of the many things the people involved have in common. Food likes, colors, reading, movies, what ever. The focus of the relationship is more on what the couple can do together, outside of sex. In BDSM relationship, often times, the focus centers more on BDSM aspects than anything more "vanilla". In losing sight of the "vanilla" aspects of yourself and your partner, you create a vacuum which eventually will break. If you are not prepared for, or expecting this breakage, it can drive you apart. 

When someone tells me they are negotiating for a BDSM live in relationship (or even play partner) I like to remind them that there is more to both themselves and their prospective partner than BDSM. Have they discussed the things that they would if BDSM were not involved. Often times, the answer is "no, I didn't think of that". Every relationship has activities outside of BDSM. Every relationship is affected by real life. These things must be taken into consideration. During a period of high stress (for either partner) often the power exchange (though still there) takes a less active role in the relationship. This is normal and should happen when stress hits. For those with children, each partner having jobs, and all the other vanilla type stuff we have to do, it often becomes overwhelming and BDSM becomes just too much "work" to bother with. Does that mean it is over for the relationship? not necessarily. Does it mean the people involved no longer are dominant or submissive? not necessarily. What it means, in my opinion, is that quite 
simply real people are struggling with real life and must prioritize. During that time, certain things do get put on a back burner. BDSM is one of those for many people. Though the power exchange may still be there, (it is after all mental) the physical showing of it may not be as frequent as it once was, or as intense. 

The best thing to do when this happens, is try to figure out where the stress is coming from. If it is obvious (work related, child related etc.) then relax. When the stress calms down, life will return to a more "normal" level. As well, try to find a balance between BDSM and the rest of who you are. No one is just a sub or just a dom, that is part of who they are yes, but there is more to them than that. Everyone has likes, dislikes, activities they enjoy, things they don't enjoy, causes they feel strongly about, whatever. Try to remember this and to interact with your partner on those levels as well as the BDSM. 

If you reach a point where you feel you are just going through the motions, it is a good idea to sit down and openly discuss what is going on both in the BDSM aspect of your life, and the other aspects. It is perfectly fine, in my opinion, to take a "break" from BDSM if that is what you feel needs to be done. Often, it is necessary to take a break, specially if BDSM has been a main focus for a long time. A person will get "burn out" eventually. 

Keep in mind that life is not static and nor are any relationships. If you keep a reality stand point to your relationship, it will make it through the "rough" spots.