For some time, the perception of healthy food is that it is tasteless, boring and bland, but if you marinate that chicken breast with herbs and spices, the taste can change considerably, and be a lot more fun. You can use your favorite salad dressing for a quick marinade, such as Italian or Balsamic, as it already has all the spices in it, or you can mix up your favorite spices and use them as a rub.
You may get bored with eating tuna salad in your sandwiches, even though tuna is far from tasteless, but if you add a little spice when you mix the tuna, you will find that there are a range of different tastes that add very little, if anything, in the way of calories. Paprika, pepper, cayenne… the list goes on. The addition of some chopped jalapenos can spice it up even more, if you have the stomach for them, and these days, the bottles of sauce on the supermarket shelves go beyond steak sauce and ketchup. New additions like piri-piri and teriyaki are a welcome break from the norm.