I appreciate what you are saying and I think we're mainly in agreement. You can't eliminate all risk and you can't guarantee success but you have a lot of ways to influence the outcome.
Using your example of depression. If you marry someone manic/depressive because you love how crazy and wild she is on her up days, her down days are going to hit you hard when you're living in the same house and sharing kids and responsibilities. So maybe that dynamic has a 50% divorce rate which could have been anticipated way in advance. On the other hand, there's always a chance that someone stable you marry will get into a deep funk years down the line and you won't be able to help her manage through that, but that maybe is a 2% probably. You can't control that 2% but you can manage to not be in the 50% and that's where your focus should be.
Using your example of depression. If you marry someone manic/depressive because you love how crazy and wild she is on her up days, her down days are going to hit you hard when you're living in the same house and sharing kids and responsibilities. So maybe that dynamic has a 50% divorce rate which could have been anticipated way in advance. On the other hand, there's always a chance that someone stable you marry will get into a deep funk years down the line and you won't be able to help her manage through that, but that maybe is a 2% probably. You can't control that 2% but you can manage to not be in the 50% and that's where your focus should be.