Your brain believes whatever it has the most evidence to support. Understand this and you can create any reality you desire in your life.
Emotions are powerful and our brain uses emotions to motivate us to action or to motivate us to inaction. Understanding how the brain does this enables us to accept both the emotions that are uncomfortable and the ones that are positive in the human experience.
Some trials I never have and never will be grateful for. However, I have learned I can still find ways to be grateful in the middle of despair and later, I am often grateful for lessons learned, for empathy deepened and a heart softened. Gratitude and sorrow can co-exist.