Barn swallows, Flies and the Wings of Perspective

The sound of my footsteps meet their cheerful song.
Their spirits swoop high, in and out of the barn, lifting mine with them.
Except it’s midsummer now. Each day that passes moves us closer to the end; to when these walls lose their heartbeat; to when there will be nothing left except their feathers and droppings; nothing but silence and sadness. I love when they come and I hate when they leave. Why can’t they just stay?
Why must pleasant things end?
The sound of my footsteps meet their discordant beat,
As their hooves slam down towards the earth, trying to shake off the attacks.
Except they can’t. It’s midsummer now. Every day passes as if there is no end; to when the air is stifled by their drone; to when there is nothing but swishing and stomping; nothing but whir and torment. I hate when they come and I can’t wait for when they leave. Why can’t they just go?
Why must unpleasant things stay?