I always try to be happy and positive as much as I can because life is just too short not to be, but one of the best things I have learned throughout my time here on Earth is that human beings cannot be happy 24/7 and that is not normal.
We may all be different people, but we all experience the same emotions from time to time and sometimes we just aren't happy. We may be sad, anxious, frustrated, exhausted, overwhelmed, etc. but we shouldn't be penalized for it. After all, what kind of life would we all be living if we were just happy all the time? We wouldn't appreciate all the good times without having the bad times.
I know for me personally, I feel obligated to be happy and all smiles every single day, but that is just an unrealistic expectation. I remember when I was back in college I would always feel so stressed and overwhelmed because I was worried about my grades and finishing assignments on time and it felt like I could never catch a break. Then, I began to realize that I was putting unnecessary pressure on myself because I wasn't letting myself experience certain feelings and did a poor job at managing them too.
We all have those days where everything seems to be going downhill, one thing after the next, but we still somehow manage to act all happy and sweet to everyone we talk to when on the inside we are on the verge of a mental breakdown. The problem with that is you are repressing those emotions inside and that is causing more harm than good. Sure, you don't want to take out your feelings on people who did nothing wrong to you, but if you don't take the time to feel them at some point, you are just prolonging the agony.
Moral of the story is, whatever you are feeling, allow yourself to fully feel those emotions and work through it instead of acting like you are fine when you clearly are not. I am notorious for doing that and trust me, people usually figure out one way or another that you really aren't fine and you are just avoiding whatever is on your mind.
Stop neglecting your feelings because they will catch up to you eventually in a much more negative way. So if you feel like crying, go ahead and let it all out. Play some sad music and let those emotions flow out your body. Trust me, you will feel like a weight has been lifted off your shoulders when you do. If you are feeling angry or frustrated, let it out in a healthy way by going for a walk or run. If you allow yourself to work through your emotions, then the good times will feel extra special and you will be even happier.
Of course, I still find myself getting stuck in that "I'm fine" stage every now again, but I am more aware of my feelings and allow myself to feel whatever I am feeling in a proper way. Tough times don't last forever, but tough people do. You just have to be strong enough to push through those difficult times that are filled with mixed emotions and you will end up even stronger in the end.