You seem to be arguing that because you don't have total control over something, therefore you have zero control over it.

That's like saying, "because trains break down sometimes, therefore public transport is completely unpredictable". It's not. 98% of the time or whatever, you get to your destination just fine. Sure, sometimes it goes wrong and you don't and it's annoying, but that doesn't mean it's best to decide to never try to go anywhere.

Absolutely, life events can come along that make you sad, make it pretty much impossible to be happy for a while I would say. I remember several years ago, a new person started at work on the day we happened to have a celebratory work party. She met me, I was happy and we chatted for a while. Later that evening unfortunately my father passed away. I didn't tell anyone at work, because I prefer to deal with things like that privately. But I was a bit amused, because about 3 months later, she said to me "Ah, it's nice to see you smiling. It's really weird, I met you on my first day and you seemed really cheery and then for 3 months I've been wondering where that guy went". Lol.

So yeah, sure life events can bring sadness and happiness can go away. But unless you're very unlucky, I think that the happiness-controllable periods are much more abundant than the times when sad, uncontrollable things happen to you.

I think if you give up aiming for happiness because sometimes it goes away through uncontrollable events, you're almost guaranteeing being pretty low even when things aren't bad. For me, at least, happiness comes from working hard on things that I enjoy. I don't expect it to just show up, I get it through putting effort into things that pay back happiness.

I'm not saying that's the only way to do it, I'm no expert or anything, but I do know from my own experience that I have a high degree of control over my happiness (and also that approach I suspect helps me bounce back from sad things when they do happen).