Alexander Graham Bell
What this power is I cannot say. All I know is that it exists and it becomes available only when a man is in that state of mind in which he knows exactly what he wants and is fully determined not to quit until he finds it.
When one door closes, another opens. But we often look so regretfully upon the closed door that we don't see the one that has opened for us.
When one door closes another opens, but we often look so long and so regretfully upon the closed door that we do not see the one which has opened for us.