I live a life most sedentary
At times with flashes of brilliance
Though mostly unextraordinary
I can impress with magnificence
I serve you well in your time of need
Though many times I'm quite neglected
After sunset, your good friend indeed
But in the daytime, I'm rejected
Yet this apparent disloyalty
Will not shatter my delicate heart
I'll stand firmly as your guide to see
Through your darkest hour, I'll do my part
What am I?