This may not be a popular response but I’m going to give it anyway. Am I always happy? No. Are there people that are always genuinely happy? Not if they’re being honest with themselves.
But as a Christian, I have peace and I have joy, among other things. As somebody said above, happiness is fleeting. Here’s an example: I have lots of health issues. I have plenty of days that I’m not feeling great although I’m still able to function, thankfully. Am I necessarily happy on those days? Of course not. But I have the peace of knowing that the ailments of this life are only temporary and that one day I will have a new body with no illnesses or physical limitations. And because of knowing this, not only do I have peace, but I have joy in knowing that this is a short time where I have to make do.
I know you may not understand if you are not a Christian. I know I may get a lot of negative feedback from people on here reading my answer. But this is my honest answer to you.