It’s very common for people to say that success feels surreal. I think upon examination there’s actually a pretty simplistic reason.
A dream is something imagined. Imagine means to “believe something unreal or untrue to exist or be so”. The more you fixate on your vision of an imagined future (simply one that isn’t real yet), you’re brain gets used to the cognitive dissonance (two beliefs held at the same time; 1. the world is the same, 2. the world should be different).
So when you spend so much time (the majority in fact), grinding, hustling, and working towards a dream and you finally achieve it, the feeling of surrealism (“not realness”) is due to the fact that your brain is now able to remove the cognitive dissonance because both reality and imagination lineup finally.
I think the connection between the height of surrealism at, or in, the moment of achievement is how large the dream is, and how fast it was accomplished. The faster it’s accomplished, the less surreal it seems. And the bigger the dream, the more surrealism.
I believe surrealism upon achievement is healthy, because it indicates the ability to hold a clear picture of reality, and maintain a large dream or vision at the same time.