A threshold means a doorstep or a frontier in English. A threshold is both the beginning and the end; we cross thresholds throughout our lives, not only when we enter our homes.
A threshold was the first thing that human hands chiseled in a forested hollow surrounded by hills, and after which Princess Libuše and her retinue named the new capital town Praha. (práh means threshold in Czech).
To cross an imaginary threshold always means to pass from one world to another, to overcome our past and to be closer to reaching our goals.
It is the decision to cross our own imaginary threshold that is often more difficult than the acts that follow.