If you haven't done this yet, Mr. McCusker recommends doing so several months prior to announcing your desire to split up to avoid letting on whatyouintendtodo.
Cheating someone certainly is, not doing whatyou said you would do in the agreement is, but not telling someone whatyouintendtodo as a result of the agreement is not.
But, ultimately, part of being principled, part of being a leader is, A, being able to describe exactly what it is that youintendtodo -- not just saying I'll sit down, you have to have a plan.