Have you ever had a day when the internet just isn't working well? When the internet is slow, it really gets on my nerves. And do you ever want to go to a site, and the site says "Page can not be displayed"? The internet isn't always reliable.
Ever have a day when your shot isn't falling? When your muscles are sore and won't work properly? Have you ever sprained an ankle or torn an ACL? Our bodies aren't always reliable.
Ever had a teammate turn their back on you? Have you ever been disappointed by a friend? Have you ever let someone down yourself? People aren't always reliable.
So what's my point?