In a large bowl, combine 2 tbsp fresh lemon juice, curry powder, olive oil, salt, cumin and garlic. Mix well.
Toss the chicken pieces in the sauce and coat well.
Allow the chicken to sit in the mixture for 20 minutes at room temperature.
In the meantime, to prepare sauce, in a small bowl mix together 1/2 cup greek yogurt with 2 teaspoons of fresh lemon juice, depending on your tastes. Set aside.
Heat a large skillet on medium and coat the pan with olive oil or cooking spray.
Cook the chicken in the pan, about 3-4 minutes per side, or until thoroughly cooked through. Remove from the heat.
To assemble pitas, take a pita pocket and slather the inside with the yogurt sauce.
Then some of the spinach and feta crumbles.
Add some pieces of chicken and then add more spinach and feta (It took me all week to perfect this arrangement).