I love the EE Cummings one.
Or this one by Roger McGough? It's about the fact that no matter how bad and final things are, there is always joy and hope in the small things and the way you share them together.
I vow to honour the commitment made this day
Which, unlike the flowers and the cake,
Will not wither or decay. A promise, not to obey
But to respond joyfully, to forgive and to console,
For once incomplete, we now are whole.
I vow to bear in mind that if, at times
Things seem to go from bad to worse,
They also go from bad to better.
The lost purse is handed in, the letter
Contains wonderful news. Trains run on time,
Hurricanes run out of breath, floods subside,
And toast lands jam-side up.
And with this ring, my final vow:
To recall, whatever the future may bring,
The love I feel for you now.