While I don't have a true motto, the thing I try to remind myself when training or racing is this:
Role model
Whether first or last, 5k or marathon, you never know who is watching. Somewhere out there someone is watching you and wanting to be like you. I am reminded of this every time I am going down a road and someone waves or says hello. Even when some car full of teens yells 'run forest run' I am reminded of this. It is right in front of me when during a race, kids are lining the sides of the streets looking for a high five. Whether it is jealousy of some or providing inspiration to others, someone is looking up to you and wants to do what you are doing.
Side note: regarding the kids lining the side of the street, take the time to give them a high five. Not only will you make their day, but you'll be surprised how good it makes you feel too!