In a bowl, whisk together the honey, lime juice, lime zest, olive oil, garlic, salt, and black pepper until smooth and well combined.
Place the chicken in the marinade and turn it a few times so every piece is evenly coated. Let it rest while you prepare the salsa, or refrigerate it for a little longer if you have time.
Combine the diced mango, red bell pepper, red onion, cilantro, and avocado if using. Add a squeeze of lime juice and a pinch of salt, then stir gently so the fruit stays fresh and bright.
Heat a skillet, grill pan, or outdoor grill over medium heat. Cook the chicken until golden, cooked through, and nicely caramelized on the outside.
Let the chicken rest for a few minutes before slicing. Spoon the mango salsa over the top or serve it on the side, then enjoy while everything is fresh and juicy.