Lay out the tortillas on a clean surface or cutting board.
Spread mashed or sliced avocado across the center of each tortilla.
Top with shredded chicken, lettuce or spinach, tomatoes, and cheese if using.
Sprinkle lime juice evenly over the filling and season with salt and pepper.
Fold in the sides of the tortilla and roll it up tightly like a burrito.
Slice in half and serve immediately, or wrap in foil for lunch later.