When you intend to do something and see that your thought is perturbed, and if after invoking God's Name it remains perturbed even by a hair's breadth, know from this that the action you mean to commit is from the evil one and refrain from commiting it. For nothing done with perturbation is pleasing to God.
Those who mourn and those who are insensitive are not subject to fear, but the cowardly often have become deranged. And this is natural. For the Lord rightly forsakes the proud that the rest of us may learn not to be puffed up.
The more a man's tongue flees verbosity, the more his intellect is illumined so as to be able to discern deep thoughts; for the rational intellect is befuddled by verbosity.
It is no small struggle to be freed from self-esteem. Such freedom is to be attained by the inner practice of the virtues and by more frequent prayer; and the sign that you have attained it is that you no longer harbor rancor against anybody who abuses or has abused you.
A person lighting a fire first has a small piece of tinder. This represents the word of the brother who has upset him. This little fire is very feeble. What significance has the word of your brother? If you put up with it you blow out the small fire, but if you begin to think to yourself, 'Why did he say that to me? I myself can answer him. If he did not want to hurt me, he wouldn't have said that and believe me, I can upset him too.' In this case, you add small pieces of wood to the fire and some other fuel like the person that lights a fire and you produce smoke which is agitation. Agitation is the movement and coming together of thoughts which stimulate the heart and make it audacious. Audacity is the taking of retribution against the person that has upset you, and this becomes insolence as Abba Mark said, 'Evil accepted in thought makes the heart audacious, but when this is revoked through prayer and hope, it makes it contrite.'
A single word made the thief pure and holy, despite all his previous crimes, and brought him into paradise (cf. Luke 23:42-43). A single ill-advised word prevented Moses from entering the promised land (cf. Num. 20:12). We should not suppose, then, that garrulity is only a minor disease. Lovers of slander and gossip shut themselves out of the kingdom of heaven.
In answer to your question as to what constitutes a happy life, whether splendor, fame and wealth, or a quiet, peaceful, family life, I will say that I agree with the latter, but will add the following: A life lived in humility and with an irreproachable conscience brings peace, tranquility, and true happiness. But wealth, honor, glory and exalted position often serve as the cause of a multitude of sins, and such happiness is not one on which to rely.
If Moses, who was a god to Pharaoh, was shut out from the Land of Promise because of one word, how much more will not the evil speech of our tongue, by which we offend and hurt both God and man, shut us out from heaven?
In words of boastfulness and self-justification there always lie concealed contrariness and pride, from which God turns away. After sinning one ought immediately to 'flee.' But you say, where? To the calm haven of heartfelt repentance.
Nothing so abets our secret destruction as conceit and self-satisfaction, or so cuts us off from God and provokes our chastisement at the hands of other men as grumbling, or so disposes us to sin as a disorderly life and talkativeness.
Think also of this: the person who is bound to earthly things may rejoice but may also be upset or disturbed or grieved over earthly things: his mind is exposed to continual changes. But the joy of your master (Matthew 25:21) is enduring, for God is unchangeable. Thus control your tongue at the same time as you discipline your body with fasting and strictness. Talkativeness is a great enemy of prayer. A spate of fluttering words stands in the way of the words of prayer. This is the reason that we shall render account for every careless word we utter (Matthew 12:36). One does not bring the dust of the road into a room that one wishes to keep clean; thus keep your heart free from gossip and chatter about the events of the day that is past.
A haughty person is not aware of his faults, or a humble person of his good qualities. An evil ignorance blinds the first, an ignorance pleasing to God blinds the second.