Alexander Graham Bell said this quote

When one door closes another door opens; but we so often look so long and so regretfully upon the closed door, that we do not see the ones which open for us.

~ Alexander Graham Bell

Man is the result of slow growth; that is why he occupies the position he does in animal life. What does a pup amount to that has gained its growth in a few days or weeks, beside a man who only attains it in as many years.

~ Alexander Graham Bell

Don't keep forever on the public road,going only where others have gone, and following one after the other like a flock of sheep. Leave the beaten track occasionally and dive into the woods. 'Every time you do so you will be certain to find something that you have never seen before. Of course it will be a little thing, but do not ignore it. Follow it up, explore all around it; one discovery will lead to another, and before you know it you will have something worth thinking about to occupy your mind. All really big discoveries are the results of thought.

~ Alexander Graham Bell

The inventor...looks upon the world and is not contented with things as they are. He wants to improve whatever he sees, he wants to benefit the world; he is haunted by an idea.

~ Alexander Graham Bell