Be not overly righteous, and do not make yourself too wise. Why should you destroy yourself? – Ecclesiastes 7:16

Matthew Poole:

1. It is not good to be more nice than wise. Beware of overstrictness, zeal, and forwardness in religion. Do not be too severe in observing, censuring, and punishing the faults of others beyond the rules of equity, without giving any allowance for human infirmity, extraordinary temptations, the state of times, and other circumstances. Or,

2. By being more just than God requires, either laying those yokes and burdens upon a man’s self or others which God hath not imposed upon him, and which are too heavy for him, of which see on Mt 23:4, or condemning or avoiding those things as sinful which God hath not forbidden [more holy than God!], which really is superstition, but is here called righteousness abusively, because it is so in appearance, and in the opinion of such persons. So he gives them the name, but by adding over-much, denies the thing, because righteousness, as well as other virtues, avoids both the extremes, the excess as well as the deficit.

3. By an imprudent and unseasonable ostentation or exercise of righteousness where it is not necessary, as if a protestant travelling in a popish country should publicly profess his religion to all whom he meets with, or when a man casts the pearl of reproof before swine, against that caution, Mt 7:6. So this is a precept that men should manage their zeal with godly wisdom, and with condescension to others, as far as may be. But this is not to be understood, either,

1. Of such prudence as keeps a man from the practice of his duty, but only of that prudence which directs him in ordering the time, manner, and other circumstances of it. Or,

2. As if men could be too good, or too holy, since the strictest holiness which any man in this life can arrive at falls far short both of the rule of God’s word, and of those examples of God and Christ, and the holy angels, which are propounded in Scripture for our imitation.

Be not wise in thine own conceit; that is, think more of men nor of ourselves than that which is written; be not proud against one another, 1 Corinthians 4:6, 2 Corinthians 10:12.

(Matthew Poole)

Why shouldest thou destroy thyself? Interesting statement. Self-destruction:

1. Beware of overstricness, &c.
2. Do not try to be more holy than God requires; that is, more holy than God.
3. Manage zeal with godly wisdom.

We do not normally connect the above points with sin, but the Wise Man said they can lead to destruction.