In the dictionary of the seeker of truth there is no such thing as being "not successful." He is or should be an irrepressible optimist because of his immovable faith in the ultimate victory of Truth, which is God.
We have arranged for ourselves a world in which we can live - by positing bodies, lines, planes, causes and effects, motion and rest, form and content; without these articles of faith nobody could now endure life. But that does not prove them. Life is no argument. The conditions of life might include error.
Even as wisdom often comes from the mouths of babes, so does it often come from the mouths of old people. The golden rule is to test everything in the light of reason and experience, no matter from where it comes.
...And these vicissitudes come best in youth;
For when they happen at a riper age,
People are apt to blame the Fates, forsooth,
And wonder Providence is not more sage.
Adversity is the first path to truth:
He who hath proved war, storm, or woman's rage,
Whether his winters be eighteen or eighty,
Has won experience which is deem'd so weighty.
All significant truths are private truths. As they become public they cease to become truths; they become facts, or at best, part of the public character; or at worst, catchwords.