They happen – unless perhaps they are unhaps or mishaps.
Following Cartier-Bresson one can aspire to hap on “the decisive moment’. Like him I only use natural light, though unlike him I succumb to cropping my pictures, often drastically.
To quote Dr. Johnson’s “A Dictionary of the English Language” (1755):
1. Chance; fortune.
‘Whether art it were, or heedless hap,
As through the flow’ring forest rash she fled.
In her rude hairs sweet flowers themselves did lap,
And nourishing fresh leaves and blossoms did enwrap.’ Spenser,
2. That which happens by chance or fortune.
‘Cur’st be good haps, and curst be they that build
Their hopes on haps, and do not make despair
For all these certain blows the surest shield.’ Sidney.
‘Things casual do vary, and that which a man
doth but chance to think well of cannot still have the
like hap.’ Knolles.
Solyman commended them for their valour in their
evil haps, more than the victory of others got by
good fortune.’ Knolles.
A fox had the hap to fall into the hands of a lion. L’Estrange.
3. Accident; casual event; misfortune.
‘Nor feared she among the bands to stray
Of armed men; for often had she seen
The tragick end of many a bloody fray:
Her life had full of haps and hazards been.’ Fairfax.
To Hap. v. n. [from the noun.]
1, To happen; to have the casual consequence.
‘It will be too late to gather ships or soldiers, which may need to be presently employed, and whose want may hap to hazard a kingdom.’ Clarendon.
2. To come by chance; to befall casually.
Run you to the citadel, And tell my lords and lady what hath hap’d. Shak.
‘In destructions by deluge the remnant which hap to be reserved are igoorant people.’ Bacon,
Had not our hap been bad – Comedy of Errors
Knowing whom it was their hap to save – ibid
Then loving goes by haps – Much Ado about Nothing
What hap may, I’ll roundly go about her – Taming of the Shrew
What else may hap, to time I will commit – Twelfth Night
More blessed hap did ne’er befal our state – 1 Henry vi
Our hap is loss, our hope but sad despair – 3 Henry vi
Be it art or hap, he hath spoken true – Ant. and Cleop.
When we shall hap to give’t them – Coriolanus
And my dear hap to tell – Rom. and Jul.
Until the heavens, envying earth’s good hap, add an immortal title to your crown – Richard ii