The expression “you don’t know what you have until it’s gone” describes how people do not bother to appreciate what they have until they are forced to. This can be viewed as an analysis or quality of people, or it could instead be viewed as what not to do. The solution to this is very simple, instead of only knowing what you have when it’s gone, know what you have before that.
The central idea in this expression is appreciation. When you appreciate what you have you realise how good it is because appreciation requires analysis. By analysing what you have you realise that it has properties that you like. By better knowing what you have you understand it better both in its small details and as a whole, which allows you to fully appreciate it. When you fully appreciate something while you have it you will have an easier time if you lose it because you will know that you fully took advantage of your time with it and did not waste any opportunities.
Instead of simply letting expressions like this be rules for how life works, let them instead be warnings to learn from. If you learn the lesson of the warning then the expression ceases to be true. You don’t know what you have until it’s gone, unless you decide to know what you have. It is a choice, not a rule of life. Blindly following what others say are rules of how life works will only make you more likely to make the same mistakes. Life philosophies, whether they be long or complex, or short or simple, should always be analysed to make sure they are true and that you learn the right lessons from them.
Take expressions like this as warnings to learn from to not make the same mistakes as others.