A person who crossdresses on occasion, for example, can talk about curbing or at least maintaining the frequency of their activity but someone closer to the transsexual side of the spectrum has nothing to negotiate because we are talking about identity instead of something which is occasional. Clearly then, compromise is a highly personal thing and depends on what each person thinks is acceptable to them. One thing I know for certain is that absolute honesty is a prerequisite as well as a complete understanding of who you are. Hence, someone who requires full time feminine expression will not be happy with someone who wants to roll it back by half.
There are those who identify as transgender who may suffer mild to no dysphoria at all. In this case they may be able to carry on a relatively "normal" relationship. However, others I know (some of whom contribute to this blog) had to transition to survive and their marriages fell by the wayside because there was no room for negotiation; they simply needed it for their survival because it is who they were.
This is a very sticky subject and a highly personal one with no one size fits all formula but, as a general rule, the stronger your dysphoria the less the chance the relationship will survive and, in those cases where it does, the onus is almost always entirely on the transsexual person to not act on their desires.
Therefore, in the sphere of personal relationships, where you lie on the gender spectrum becomes crucially important.