Begin by preparing the chicken: In a bowl, combine lemon juice, olive oil, finely chopped fresh herbs, minced garlic, salt, and pepper. Add the chicken breast and let it marinate for at least 20 minutes.
Preheat the grill (or grill pan) over medium-high heat. Meanwhile, preheat the oven to 400°F for roasting the sweet potato.
Wash the sweet potato thoroughly, then cut it into cubes. Toss the cubes lightly with a pinch of salt, pepper, and a drizzle of olive oil.
Spread the sweet potato cubes on a baking sheet and roast in the preheated oven for 20-25 minutes or until tender and slightly caramelized, stirring halfway through.
Grill the marinated chicken breast for about 6-7 minutes per side or until fully cooked and internal temperature reaches 165°F.
Assemble the dish by placing a bed of mixed greens on a plate, top with the sliced grilled chicken, and add the roasted sweet potato cubes. Optionally, drizzle any remaining marinade or a little extra lemon juice over the greens for an added burst of flavor.
Serve immediately and enjoy your fresh, flavorful meal.