I totally agree with you and normally stable source of income is suppose to make one not to sell when there is fluctuation and discipline, target and determination play an important role here. Some people can do sell there investment even when there is no fluctuation in the market because they are not discipline, they don't have target but if someone has a target and he or she is discipline whether there is stable source of income or not they will keep holding accumulating because they will be determined to hit there desire target that is to say that selling when there is fluctuation is a mindset and a choice.
Knowledge brings needed resolve to continue to hodl appropriately and not drop your bags on the get-go.
Fluctuations are normal, dips and corrections - too.
They are part of the process
Knowing Bitcoin value keeps increasing long term by just simply looking on a zoom out chart makes it easy to hodl long term without the need to know more just for the sake of hodling.
It’s not bad also to partially take profit and re-invest later on as part of rewarding yourself so that you will not think on your investment most of the time especially when the price is increasing.