By instructing the Englishman to go and try, the Englishman is motivated to continue on his journey toward his Personal Legend.
The Englishman has tried to accomplish his Personal Legend by doing research and asking for someone to just give him the answer of how to turn lead into gold. The Alchemist, instead of just giving him the answer, tells him that he needs to go and try. This is an important lesson. In life, you can research and read about other people doing what you want to do, but until you go out and actually try to do it yourself, you're not accomplishing anything.