There is a hormone called dopamine which is also known as the feel good, reward chemical.
Your body produces dopamine once you have completed a task, achieved a goal or have a win.
Problem is...
Your brain doesn't know if the win is imagined or real.
So, when you mentally masturbate (aka talking big about your plans and what you intend to achieve and getting people's hype responses), your brain sees it as a win for that goal and triggers dopamine.
Then...
It relaxes your desire and allocates more energy to other things since you have already achieved that particular goal.
It is like young guys who use porn and masturbation as way to get sexual satisfaction instead of going out to meet women.