I think what you discover on the path of self-discovery/self-improvement is that peace is more important and far easily more attainable than Happiness.
Think of happiness as a Crane that flies off in the spring to breed and comes back in the summer after the work is done. Happiness isn’t meant to be sustainable or stagnant, it’s meant to fluctuate; quite like the waves and ripples of a river or a stream.
Happiness is an emotion; like sadness, jealousy, anger etc. But, peace on the other hand, is a state of mind; it’s an attitude.
Monks(probably the most peaceful people on earth) don’t go up into the mountains in pursuit of happiness or joy, rather peace. Peace cannot be attained, because it’s already within you, and it also cannot be lost, precisely for the same reason.
Thus, the pursuit peace is more sensible, because it depends on nothing. You don’t need to run off to a different country, get a romantic partner, or get that job to be peaceful, rather these things are more likely to take it away; not that I’m discouraging the pursuit of these things, I believe they are also a part of life and are natural experiences meant to be faced. But, to be peaceful all you need to do is close your eyes and breathe, it’s as simple as that; and in that moment; no feeling, no emotion can take control of you, because you do with emotions what should be done; you feel them, without distractions and they leave you like the cranes that fly off in the spring.
Peace is the easiest thing to attain, but it is quite a paradox as you cannot attain what you already possess. I feel the better word to use would be rather ‘discover’. Peace should be discovered not in the most quiet of mountains, but in ourselves, in our own minds.
We as humans want something sustainable; and then we choose to pursue happiness, we choose to pursue a Crane with our bare feet. I say, sit with it, whatever you feel and be at peace.
Happiness isn’t sustainable, it was never meant to be. So, give yourself a break and stop feeling bad for feeling bad.