How does mediation lead to happiness?

I have recently taken inspiration from Mark Manson after reading "The Subtle Art of Not Giving a F*ck". The following points from Mark's writing really resonated with me as a mediator.

1. Emotional pain lets you know in which ways to improve your life. It teaches us.
2. Adversity and failure are helpful and essential for developing.
3. Happiness requires struggle, and it comes from solving problems.
4. Negative emotions are a vital part of emotional health, and can be channeled to your ultimate benefit. A simple example is instead of asking questions like "How do I stop suffering?" consider asking yourself instead, "Why am I suffering? For what purpose?".
5. You are responsible for your life, regardless of fault, because you can always decide what you make of your circumstances.

In my work as a mediator I am working with people daily who are grieving, angry, sad and anxious. I have found that if a person is capable of seeing a relationship break down as an opportunity to improve themselves, learn, adapt and become a problem solver, starting with reaching agreement about the legal terms of the end of their relationship, they are well on their pathway to future happiness.