Answer:
They are the shore's gallant knights.
I have joy in bringing two together, but darning my existence! My life hangs by a thread, filled with ups, downs and resistance!
Everybody's got one.
Its days are numbered.
We are two brothers on opposite sides of the road, but we never see each other. Who are we?
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?