It may be said that a man who does this will lay himself open to be deceived, and that in many cases his confidence will be misplaced.

That is a small matter; it is far better for him that he should sometimes be deceived as a result of his trust in his fellows than that he should save himself from such deception by maintaining a constant attitude of suspicion.

Besides, confidence begets faithfulness.

A man who is trusted will generally prove himself worthy of the trust, whereas a man who is suspected is likely presently to justify the suspicion.
If a man finds in himself the tendency towards avarice, let him go out of his way to be especially generous; if he finds himself irritable, let him definitely train himself in calmness; if he finds himself devoured by curiosity, let him deliberately refuse again and again to gratify that curiosity; if he is liable to fits of depression, let him persistently cultivate cheerfulness, even under the most adverse circumstances.
In every case the existence of an evil quality in the personality means a lack of the corresponding good quality in the ego.

The shortest way to get rid of that evil and to prevent its reappearance is to fill the gap in the ego, and the good quality which is thus developed will show itself as an integral part of the man's character through all his future lives.