Yes you can leave for any reason. By mate, I assume you mean husband or wife. Traditional vows says in sickness and in health. That is a large undertaking. This leads to so many different levels of what sickness means. It could be impairment too. So here’s my thing on sickness, yes you are to be there no matter what. However I’m not going to lie and act as if I haven’t thought about what happens when your mate has a condition that they can fix or get help with but refuses?! Does the same rules apply? Yes and no. You shouldn’t off the bat pack your bags but dealing with selfishness especially when whatever illnesses puts stops and halts in the family structure is not cool. Communicate. Offer suggestions. Put in some effort. If you should leave on those premises than be sure you can say that you did ALL you can. Hollywood marriages don’t seem to apply the ALL clause. Marriage is work and it’s not for everyone. However you are one but the power you have over someone else stops at the tip of your nose. You can’t make anyone do what they don’t want to do.
Put some thoughts into what you’re asking me and spend some time with why you feel like it’s time to possibly leave. Subtract any anger and get to the real issue. Could it be that it has more than just a possible fixable health concerns? Try to find the reason you got together in the first place. Is whatever is going on non negotiable? Can you live with your decision? You alone will have to take on the brunt of whatever decision you make. This isn’t just about what is ethical or just. This is about your willingness or your partner’s willingness to work together. Don’t just throw away a marriage due to being overwhelmed. If this sickness isn’t something that is curable or something controllable, is there a support group for it? If you have others going throigh the same thing than maybe just maybe it could be an outlet that can give you the feul you may need to continue loving and making things work.