The laws of math doesn’t apply in relationships. If both partners make their efforts in half measures, it only adds up to unhappiness, somebody is going to come up short and that will cause resentment, which will lead to problems.
When the going gets tough, lean on each other and work through it, rather than pulling back to 50%.
You owe it to your life partner to give them your all.
And boys if you are married, remember one thing. “Happy WIFE, Happy LIFE”