True - the greater the loss, generally the harder I'll try to prevent it. However, I'll make just two observations.

One: of course the potential loss from a divorce is often not equal for both partners, meaning on some level they may - to your own point - be unequally incentivized to prevent a break-up.

Two: In some unfortunate situations it may not matter if you try even harder to prevent a break-up if your partner has made up their mind. Or, if you stand to lose more, concessions can be squeezed out of you in an unfair way. Obviously you do your best to avoid a partner that would do anything like this, but in the end you can't be sure for a variety of reasons.