Answer:
In many years, not much has happened. In many minutes, a lot has happened. In one second, everything has happened.
A leathery snake, with a stinging bite. I'll stay coiled up, unless I must fight.
It is more feared than fear itself, And no one can escape it. It takes no sides and does not judge, it does not know to hold a grudge. It is the most clearest result, Of how life beats you by default.
Always old, sometimes new. Never sad, sometimes blue. Never empty, sometimes full. Never pushes, always pulls.
I am nothing but holes tied to holes, yet am strong as iron.
People take me on walks and I run and have fun. What am I?