Although the question has the word "marriage" in the title, it is really about any most important relationship in a founder's life, be it husband/wife, fiancee, boyfriend/girlfriend, partner or significant other.
During my first start-up, there were times when I thought the pressures of the business were going to result in my wife leaving me. Thankfully she didn't and we got to a reasonable exit (for the business!) without a matrimonial disaster.
This subject obviously has a lot to do with work/life balance and I note there is a question on that subject, but as I get into my second start-up, I'm interested specifically in how other successful founders maintain healthy relationships with the one they love. A great example on husband and wife startup give-and-take can be seen in Jason Cohen's article and his wife's response - can anyone else share their personal stories, provide helpful tips or point out relevant articles?