How do you justify taking unpaid vacation as self employed?

Since I don’t wanna be potentially replaced by competition I haven’t taken vacation in years (that was not problem before since I was not that busy and could rest enough every day to have free morning or afternoon) and I don’t won’t to refuse any projects to miss on money I can’t imagine taking vacation, because I’m not gonna lose only vacation expenses, but also similar amount in lost income for every day I would not work.