Greek Yogurt Chicken Salad with Grapes and Celery

cooked rotisserie chicken (skin removed)

Plain Greek yogurt (to taste (I used between 1 cup - 1.5 cups))

Poultry seasoning (to taste)

Black pepper (to taste)

celery stalks (diced into small cubes)

red grapes (halved)

Lemon juice (optional)