The harmony of God is hidden within a diversity of personalities.
Some men tell me: “I don’t see eye to eye with my wife; we have opposite personalities. She has one temperament, I have another! How can God do such strange things? Couldn’t He have arranged a few things so that couples matched, and they were able to live more spiritually?” I tell them, “Don’t you understand that the harmony of God is hidden within a diversity of personalities? Different temperaments actually create harmony. Alas, if you had the same personalities! Think what would have happened if, for example, you both got angry easily: you would destroy your house. Or, consider if both of you had mild temperaments: you would sleep standing up! If you were both stingy you would get along, yes, but you would both end up in hell. Likewise, if both of you were open-handed, would you even be able to keep your house? No. You would disperse everything, and your children would be turned out to the streets. If a spoiled brat marries a spoiled brat, between themselves they get along fine, right? But, one day someone is going kill them! For this reason God arranges it so that a good person marries a spoiled brat, that the latter may be helped. It may be that he or she has a good disposition, but was never instructed correctly when young.”
Little differences in the characters or personalities of spouses actually help couples to create a harmonious family, for the one completes the other. In a car it is necessary to use the gas pedal to go forward, but also the brake pedal to stop. If the car only had brakes it wouldn’t go anywhere; and if it only had gears, it wouldn’t be able to stop. Do you know what I said to one couple? “Because you are similar, you don’t match!” They are both sensitive. If something happens at home, both of them lose it and start-up: The one, “Oh, what we suffer!” The other, “Oh, what we suffer!” In other words, the one causes the other to lose hope even more! Neither is able to comfort the other a little by saying, “Hold on, our situation is not that serious”. I’ve seen this in many couples.
When spouses have different personalities it helps in the raising of children even more. One spouse wants to put on the brakes a little, but the other says, “Give the children a little freedom”. If they both are overbearing they will lose their children. If, however, they leave them on their own, again their children will be lost. Therefore, when the parents have different personalities, the children enjoy a certain stability.
What I’m trying to say is that everything is needful. Naturally, one’s personality quirks shouldn’t go beyond their limits. Each spouse should help the other in his own way. If you eat a lot of sweets, you’ll want also to eat something a little salty. Or if you eat, let’s say, lots of grapes, you’ll want a little cheese to cut the sweetness. Vegetables, if they are very bitter, are not eaten. But a little bitterness helps, as does a little sourness. Some people, however, are like this: If someone is sour, he says: “Let everyone become sour like me.” And whoever is bitter says, “Let everyone become bitter.” Likewise, those who are salty say, “Everyone should become salty.” Bridges aren’t built like that! 
“Crowns are wont to be worn on the heads of bridegrooms, as a symbol of victory, foretelling that they approach the blessing (of Marriage) unconquered by pleasure.” St. John Chrysostom, Commentary on the First Epistle to Timothy, Homily IV, PG 62, 546).
Elder Paisios means that this work is done by the spiritual father and it is effective, only as long as the two spouses have the same spiritual father, in order that the sanding happens “using the same tool”.
Obviously, the Elder is using a metaphor: “Bridges (i.e. relationships) aren’t build like that!”