Difficult

dif·fi·cult  

/ˈdifiˌkəlt/

Adjective Needing much effort or skill to accomplish, deal with, or understand. Characterized by or causing hardships or problems.

Synonyms hard - heavy - trying - tough - arduous - laborious What a definition of the word by Wikipedia, amazing!! One Needs much effort or skill to accomplish, deal with, or understand the thing, situation or... So if one will get those skills, nothing remains difficult.  Great yet simple thought.