I’ve heard of this phenomenon of feeling depression after a goal a few times but have never experienced it. Here’s why I think I don’t experience this:
- My goals are typically so difficult that at the actual moment I achieve them, I only register it on the intellectual level because I’m too exhausted to feel anything at all. Example: finishing my half-Ironman. There’s no elation or depression because you don’t have feelings at all for a couple days. It took two weeks after the school one last year, that goal fucking sucked..
- I understand at a deep level that it’s not about the destination. Anticipation of accomplishment is the fun part.
(NB: I still visualize the moment of completion as being very emotionally satisfying and all the people from Evangelion are clapping and a penguin is saying “Congratulations!” but I don’t actually expect this. Honestly the real satisfaction comes later as a sense of underlying confidence and self-esteem and the resilience that comes from proving that people who treat me like shit, or have done, are just plain empirically incorrect.) - I’ve always had my next priority goal picked out already so there has never been a period of directionlessness between goals.
- My life has been and is generally quite hard due to the reasons we generally complain about on the internet (straight, white, Christian, male, high IQ, Asperger’s, far-right politics). It’s possible that the ennui of an otherwise easy life plays a part in taking away the feeling of accomplishment from striving in the particular.
- It could just be another weird symptom of Asperger’s.
- It’s also possible that it’s going to hit me one of these times and it just hasn’t happened yet.
Aeoli Pera 
This year I got the insight that “depression” isn’t a case of feeling the “sads”. Depression is the feeling of not wanting to do anything but lay on the sofa. I was over training and didn’t realize what the doctor was actually asking me.
I endorse this comment.