For most people, setting and achieving goals is a serotonin boost.

I'm more of a bigger picture kind of person. My entire purpose in life is to make humanity move forward and hopefully a little better than it was. If I died tonight in my sleep it would be unfortunate in a lot of my better laid plans would never happen but all the stuff that I've done at this point all the people's lives that I've impacted they would still hopefully be somewhat better for that.

In the time scale of a true existential crisis, as far as we can tell humanity is doomed anyway. So I'm here too collect my share of serotonin and raise some kids who will hopefully collect their serotonin. And all of us together are here to make sure that other people get to collect their serotonin. We're little cogs in the giant machine of humanity.

Life is to live in the happy moments and ignore the dull and crappy stuff that's in between. If you're not getting those happy moments seek help they're out there for you. You just need some help from a professional to better be able to experience them.