Children of parents who hide all emotion learn that adults don't feel — or shouldn't show feeling. Brief emotional moments witnessed (sad about a death, moved by a film, frustrated about a setback) teach that emotions are normal human experience.
What works
Brief explanation appropriate to age. 'I'm sad about Grandma. It's okay; I'm allowed to be sad.' Then continue the day. Don't burden child with managing your emotions; don't pretend nothing happened.
Modelling matters more than instruction. Children develop emotional regulation by watching adults; hidden emotion produces confused adults.