The “Effect or Affect?” Conundrum

When should the word “affect” be used rather than “effect?”  Despite my English-Majorness, I’ve never mastered this rule.

I understand affect as noun that are refers to someone’s countenance (e.g. “he has a flat affect”) or as a transitive verb meaning “to make a false display of” (e.g. “he began to affect a British accent”) but the verb baffles me.   Wiktionary’s explanation just left me more confused, especially since it lists “effect” as a synonym of “affect.”  WHAT??

Saying “I want to affect policy in Washington” means I want to influence policy, yes?

And “the devastating effects of this policy” uses “effect.”

But for “this policy will negatively effect/affect people with disabilities,” which should be used???  AGHHHH!

English is a very difficult, irregular language!

Why?  Why is our grammar and usage such a mishmash??

Because of this:

This pie chart from Wikipedia displays the origins of English language words.  French and Old Norman: 28.3%, Latin, including modern scientific and technical Latin: 28.24%, Other Germanic languages (Old English, Dutch, Old Norse): 25%, Greek: 5.32%, No etymology given: 4.03%, Derived from proper names: 3.28%
This pie chart from Wikipedia displays the origins of English language words. French and Old Norman: 28.3%, Latin, including modern scientific and technical Latin: 28.24%, Germanic languages (Old English, Dutch, Old Norse): 25%, Greek: 5.32%, No etymology given: 4.03%, Derived from proper names: 3.28%