The brain 🧠 is an organ and can suffer from pathologies as other parts of the body. Our brain is programed to seek pleasure and avoid pain. When we are in normal status, of course we can have ups and downs and be happy some times and sad other times. However, for some reason the brain will create patterns that mostly bring the person the pain and less reward - which translates into people that don’t see fun in any activity: family, friends, job - think this becomes a desease because the person normally cannot escape the loop (alone). Considering that our “circuits” are synapses working via chemistry .... some rebalance is needed that is why psychiatries call it a pathology and treat with therapy and/or pills. Of course think those are minority of cases and to normal life it is okay to be sad for a while and work for learning and changing the situation - so agree with you we should be in control!!!!!!