I try my best to keep happy, to keep smiling, to keep being optimistic, and to love first. Even if you’re having a great day, someone’s sharp words or actions can cut through this happy bubble of a space that you’ve created around yourself. What should we do then?

There are a few things we can do: keep pushing through, try to process it and struggle to keep yourself on the path of happiness you were in, or break and let everything damage you. I’ve done all three. Is it healthy to brush things off and not deal with things that hurt you? No, but it is healthy to create a habit of not letting things get to you. It depends on each person, but there are times you feel like you need to break and let God comfort you and give you peace, letting you know what the real truth is. But it’s also good for us to know what the truth is when other sounds try to interrupt a beautiful day that He has given us. 
Personally, I’ve been trying to work on patience and endurance. People say false things all the time, and I’ve been learning to push through, and if I feel like breaking, I try my best to let God into the conversation I have in my mind. As of very recently, life’s been pretty good and I basically just acknowledge to myself that some people don’t know better. God can deal with them later. It’s just another headache and worry that I don’t want in my life. 
Find what puts you in a happy place with God. I can do various things: putting on some fun jams, watching funny videos, reading, writing out my thoughts (God intervenes every time and lets me know the truth), going on a walk, or just some alone time. Discover what puts you in a better mood and connects you with God. 
Conflict isn’t something we desire. If the world was perfect, we’d be anything but human. But when conflict does arise, it can be difficult to think before speaking or acting. Breathing and letting things go or speaking calmly is a wonderful concept I’ve tried to exercise. Let them believe what they want, and know the truth yourself. 
The classic question comes up “What would Jesus do?” I remember seeing a brand floating around on Facebook and they created a wristband (same style as the W. W. J. D. ? one) that had the letters H. W. L. F. on it. I was confused seeing the two wristband bracelets side by side. The second set of letters stood for “He Would Love First,” and I try to execute that. 
We can love first, whether that be ourselves or another person, and we should always try to act Christ-like, even when it is difficult. If you let God sink in (He is love), then you’re much likelier to be a happier person, to feel more loved, even when the outside world isn’t being so lovely. 
It may feel like people don’t understand you, but they don’t have to. God does and He sees all the little things. Don’t let stuff get to you, don’t let them steal your joy, let God make you smile and help you to love first. 
~The Inspired One