Weed (THC specifically) impacts dopamine levels.

"What Happens When Dopamine Levels Rise Due To The Effects Of THC?

Elevated dopamine levels trip the brain’s reward system, causing feelings of pleasure, satisfaction, and achievement. Dopamine can also make time seem to go slower as mental activity speeds up, with increases to libido, energy, and focus.

But, if dopamine levels in your system stay too high for too long, the body will close off some dopamine receptors for a while, even after your high wears off. 

This drops dopamine synthesis in your body, blunting the pleasure you would normally feel from other things in your life like food, physical contact, hobbies, and achievement.

This lack of enjoyment from other activities is a common symptom experienced by heavy marijuana users and those who abuse other drugs like opioids or amphetamines."

https://www.arkbh.com/illicit-drugs/marijuana/dopamine-levels/

So, yeah, like others have said, take longer breaks.