The seven blessings which draw divine blessings for the duration of the couple's married life commence with a blessing over a cup of wine.
While every person projects a certain persona, wine has the ability to reveal the person behind the façade, the hidden elements of the person's personality. After imbibing a drink of wine, people tend to reveal the personality which lurks beneath the surface for better or for worse. What an appropriate metaphor for marriage, when two soulmates resolve to accept each other unconditionally; not only the persona projected by the other, but also the hidden and subconscious elements of their spouse.
Additionally, wine gladdens the heart.1 But in order to produce this heart-gladdening beverage, a grape must be crushed. Married life is full of crushing moments the key is to together overcome those challenging occasions, which leads to new levels of love and happiness.
Birkat Hamazon