About 10 years ago when reading about how gratitude leads to happiness, it didn’t really make sense. The thinking was, “but, how?”
A personal key discovery was reframing. Meaning, when you practice being grateful, just like a skill in a sport you get better. So, when the challenging times do come your thinking speeds up and through being grateful you can put things in a positive frame a lot faster. This in turn creates a path to overcome challenges and adversity quicker, than perhaps previously.
Is it easy to develop this skill? Not necessarily. As mentioned it takes practice and consistent practice at that. A powerful skill to learn.
By the way there is nothing wrong with being sad, mad, frustrated, etc. It’s part of being a person. Gratitude is a way we can bounce back to experience good moods and happy times.