If you can't heal the wound, don't tear it open. 30 Dan. Pr.
If you can't pay for a thing, don't buy it. If you can't get paid for it, don't sell it. So you will have calm days, drowsy nights, and all the good business you have now, and none of the bad. Ruskin.
If you command wisely, you'll be obeyed cheerfully. Pr.
If you criticise a fine genius, the odds are that you are out of your reckoning, and instead of the poet, are censuring your own caricature of him. Emerson.
If you desire faith, then you've faith enough. Browning.
If you desire to enjoy my light, you must supply 35 oil to my lamp. Pr.
If you dinna see the bottom, don't wade (i.e., don't venture, if you can't see your way). Sc. Pr.
If you dissemble sometimes your knowledge of that you are thought to know, you shall be thought, another time, to know that you know not. Bacon.
If you do anything for the sake of the world, it will take good care that you shall not do it a second time. Goethe.
If you do not err, you do not attain to understanding. Goethe.