Actually confidence is a tool while many failed and some too with hood confidence overcome the force of selling off their holding, but there is one aspect I do consider while most holders sell off their Bitcoin the area of unforseen circumstances and loss of target over speculated period of time, some holder have some speculation while they hold that certain period what they are holding should be at a certain price and when the reverse become the case and their alternative failed them they are left with no option than to sell what they have. Though it's very wrong shall but to say when the need is not available the available become the need could be their situation at that point because some is not as a result of clear eye but been instigated by unknown factor beyond some emergency fund mostly life threatening issued.
An important aspect is discipline and I think this is what you are trying to point out, it is a quality that every investor needs to have to be a successful bitcoin holder because the journey is not always rosy and it will take a strong mind to withstand and overcome the selling pressure when there is a dip in price during bear season. A disciplined mind will achieve a whole lot over a long period of time with bitcoin, there is no need to panic and sell when things are not going well you just have to keep in mind that there will be ups and downs during the journey.
To avoid selling we need to strategize and plan our investment properly and not invest money we intend to use for other things and we should always set aside emergency funds to cater for unexpected expenses to avoid liquidating assets prematurely but most investors take it for granted and feel it’s not a necessity.
What determines or make one a good long term or successful Bitcoin holder, is not only having the ability to withstand and over comes selling pressures when there is a dip in price during bear season it is also has to do with over coming the temptation of selling even when in profits during a bullish season, there are weak hands that can sell there Bitcoin during bullish season and not only during a bearish season.