The underlying, interdependent factors are: 1.  stable institutions;  2.  a compelling economic policy strategy and policy mix, with straightforward, credible rules that are understood and observed by all players;  3.  the firm understanding and the credibility that macroeconomic policy, in particular fiscal and wage policies, will be adjusted whenever necessary; and  4.  sound economic fundamentals.
In general, I would caution a simple transfer of conclusions from one country’s experience to any other country. However, I absolutely believe that these principles play a vital role in any fixed exchange rate regime, including currency boards, such as Bulgaria’s arrangement.