Why does brain fog occur after fapping, but not after sex?

Often wondered this myself. I've heard there's a difference in your jizz if you rip one out yourself vs getting it on with someone else, but I don't fully understand why/how. Following.

Because when you fap your testosterone goes down, while after sex it may increase or remain the same

I think it is because there are good chemicals like seratonin that increase while bad ones like cortisol decrease. This can only be achieved by doing an intimate activity with a partner like sex. Sex is also a challenge so there is a feeling of triumph especially if she is satisfied. It is also more physically demanding. There is no challenge to overcome in pleasuring oneself, once it is done there really is only emptiness.