dopamine spikes

Dopamine spikes are like sudden infusions of capital into a flat economy -sort of like IT money into Bangalore - there's inflation, and if you're not careful, a depression follows.
So, be wary of highs..

Also, since attention is biased more towards sticks than carrots**, negativity is a much bigger force than commonly acknowledged.
And since the brain reinforces what is already inside, negativity leads to more negativity. Depression is next.
A solution is this : a habit of positive thinking is needed. A habit specifically because habits are more un/sub-conscious and conscious doing is hindered by what's already on the mind.
Enter God/religious/spiritual practices/Happy place/ etc - there are different mechanisms

** that's why everyone's always cribbing, that's why you don't know the value of something until you lose it - your brain is tuned to look for negatives all day long, not at how things are working correctly