Relax. Under the current system we already owe taxes on bitcoin, stocks, bonds and other assets each year even if nothing has been sold. Its currently not solely based on changes in asset values, but on (a) assumed return percentages per asset class you invest in or (b) if you elect to do so, based on actual returns for your portfolio (incl. unrealised returns). NL is a great country to live. Investors and non-investors alike know that. No need to get too dramatic about this.