Lemons are my secret weapon in cooking.  A bit of lemon zest or juice will perk up anything from a cold pasta salad to a glass of sparkling water and all things in between.   I add lemon zest and juice to chicken soup, mashed potatoes, baked chicken, sauces, etc.  Just try it in your favorite recipes to give them some "sass!"
And here's another tip:  A few drops of lemon juice added to a pot of simmering rice keeps the grains from sticking together.