Some quotes that are my favorites and that I use on a daily basis while doing this job:
"Perseverance is the hard work you do after you get tired of doing the hard work you already did. " Newt
"Perseverance is a great element of success. If you only knock long enough and loud enough at the gate, you are sure to wake up somebody." Henry Wadsworth Longfellow
"Of all that is good, sublimity is supreme. Succeeding is the coming together of all that is beautiful. Furtherance is the agreement of all that is just. Perseverance is the foundation of all actions. " Lao Tzu
"When you come to the end of your rope, tie a knot and hang on". ~Franklin D. Roosevelt
"When people show anger and malice , listen for truth in the message, ignoring the way it was said"