You are right, there is no guarantee anywhere that  following the teachings of a trading mentor strictly will result in regular profits, professional traders still record losses. It is not even safe relying on the knowledge you gathered from one source, trading involves lots of learning from reliable sources.  The essence of learning trading from an expert or other sources  is to gain the right knowledge which you can use to form your strategy and boost your confidence as a trader. The amount of knowledge you have at your disposal have the chances of influencing your decisions while trading but there are no guarantees for regular profit or loss. This is why trading is very risky, the outcome of a trade cannot be predetermined accurately.