Maybe entering the portal takes as much energy as it would take to climb the long way? If the other end is on the moon you have to enter at 10km/s or something else you fall right back out. Warning: I am not responsible for damage caused by extreme tidal forces.

Curiosity.

Your most fundamental motivations are inherently irrational/instinctual, but once you know what they are you can pursue them more deliberately. Nobody can decide for you what the meaning of your life is, you have to discover it through experience and introspection.