You might have to spend time caring for your unwell spouse, as happened to me. Of course, it could be the other way about. In some cases, they both fall ill and have to take turns looking after each other.
When you are young and healthy, you don't believe the 'in sickness and in health' bit nor the 'till death do us part' bit. I insisted on changing the latter to 'as long as we both shall live' but it's really the same.