Why wasn’t I good enough for him?
Life will be miserable if you think like this.
In one simple sentence, you’ve managed to cram together an invalidation (why wasn’t I) , a value judgment (good enough), and a personalization (for him.) Let me help you see it another way.
First, you can’t take this personally. It’s not even about you. I know this is difficult to accept, but you have nothing to do with what he wants or doesn’t want. His personal preferences do not speak to your quality in any way whatsoever.
While you’re at it, stop judging yourself. This has absolutely nothing to do with you being “good enough.” Your value as a human being is not connected to his romantic whims.
Finally, don’t invalidate yourself. This isn’t a failure on your part. There is no reason to frame this negatively. I know it hurts. Believe me, I know how much unrequited feelings suck, but don’t let the pain trick you into believing you deserve it.
Strip away the invalidation, the value judgment, and the personalization, and “why wasn’t I good enough for him” becomes simply, “he prefers something else.”
That’s it, really. He prefers something else, and it’s not a reflection upon you, nor is it under your control.
Accept that. Learn to think this way. You’ll still feel the pain, but it won’t be agony. It will be bittersweet instead.