A good response to the statement, "You can't be happy all the time," could be:
"You're absolutely right. It's true that nobody can be happy all the time. Happiness is just one of many emotions we experience in life. Like everyone else, I have my ups and downs, and I believe that's a natural part of being human. Emotions are complex, and they give depth to our experiences. What's important to me is striving for overall well-being, finding joy in the little moments, and learning from the challenges life presents. Embracing the full spectrum of emotions allows me to grow, appreciate the good times even more, and develop resilience during difficult times."