At C1 you handle the most subtle article patterns: abstract nouns with and without "the", generic plurals, and idiomatic fixed phrases.
Abstract noun (general)
Honesty is the best policy. (general concept, no article)
Abstract noun (specific)
The honesty she showed was remarkable. (this specific honesty)
Body of knowledge
Economics is fascinating. (no article with field of study)
The with abstract nouns when specified
No article (general)
Beauty lies within.
Time heals all wounds.
Knowledge is power.
+ the (when defined)
The beauty of this place stays with you.
The time we spent together was wonderful.
The knowledge she has acquired is impressive.
Generic reference: three patterns
Plural noun (most common)
Dogs are loyal animals.
A/an + singular (any one)
A dog is a loyal animal.
The + singular (the species)
The dog is descended from the wolf. (academic/scientific)
All three express "dogs in general" but with different shades: plural is neutral, a/an highlights one example, the + singular is the scholarly/scientific style.
Fixed phrases without articles
Idiomatic — must be memorised
at + place/time
at school, at work, at home, at night, at noon, at sunset
by + means
by car, by hand, by chance, by accident, by heart, by mistake
in/out + state
in trouble, in love, in danger, out of work, out of breath
on + activity
on foot, on holiday, on purpose, on TV, on duty
Idioms
hand in hand, day by day, face to face, side by side
Articles in headlines and lists
Headlines drop articles
PM resigns after scandal. (= The PM resigns)
News telegraph style
Man bites dog. (compressed — full: The man bit a dog)
Bulleted lists
"Tools needed:" — saw, hammer, drill (no articles in list form)
Recipes / instructions
Add salt and pepper. Stir until smooth. (often dropped)