What you think not only affects you, it affects those around you. It can even affect those not in your immediate presence.
Your consciousness also affects matter. Did you know that a scientific experiment is affected by the person observing the experiment?
Srila Prabhupada said the world would become Krsna conscious if one percent of the population became devotees. This change would not take place only because of the spiritual activities of that one percent; it would also take place because of the spiritual consciousness of that one percent.