We have many challenges in life. There are opposite force in various form and types. I think of a challenge as an enemy so, the enemy of peace is war for example. And the enemy of silence is noise. If they are not helping you they are against you. If you are not eating you are starving. A kind word and a smile verse, being mean with a frown.

Sweet enemy of sour

Soft enemy of hard

Right enemy of left

Up enemy of down

Light enemy of dark

Correct enemy of wrong

Fire enemy of ice

Wet enemy of dry

Full enemy of empty

Vacation enemy of work

Friend enemy of foe

Straight enemy of curve

Knowledge enemy of ignorance

Tame is the enemy of wild

Solid is the enemy of hollow

There is an equal and opposite force in all our life. An enemy to every foe and good to every bad feeling lucky do not feel shame. Getting around the limits and the environments boundary is the challenge.