It’s called grief. Let yourself grieve for a stillborn dream.
Grief is like that. It gets triggered. You think you’re over whatever happened then, whamo, the light slants across a table just so and the waterworks turn on.
There’s no rationalizing your way out of it. It simply is. Let it pass through you like a storm.
I can only tell you that the storms get less frequent and less intense.
Disclaimer: I am not a psychologist, nor do I play one on TV. Take everything I say with a grain of salt and call me in the morning.