1 million is 0.0142857143% of 7 billion. More than likely our lives will not directly (personally) impact even 1 million people; which means over 99% of the population will know essentially nothing of our life on a personal level. It stands to reason therefore, that our labors should be primarily towards God who does directly observe our labors. Sure, the names of American Presidents are known by millions, but that doesn't mean they directly (personally) impact the people who know their name. People are impacted by people the talk to daily, weekly in a home or church, or co-worker. A good book may shape someone, but most of the stuff we read wears off in a month or two, we need that repeated guidance which comes from conversations, friendships that are given by a spouse, parent, or close friend. Your faith and endurance will renew me much more than some book I read 9 years ago. A book will not listen to my frustrations or struggles, but a spouse and parent will. My final point is that we should labor diligently (not because mankind notices, because 99% will not notice) because God sees, and God knows our faith, love, and motive to glorify Him in that labor and ministry.