Your Spouse Should Be Your Best Friend. From the time you say, "I do" your spouse takes priority position in your life.

Every other relationship you have with other people should be downgraded to a lower position. It is improper for a
married person to have a closer friend or a closer relationship than a spouse.

Apart from God your spouse is
the most significant person in your life and should therefore take the position only lower to God. By default, your spouse should be your best friend. All other friends, especially members of the opposite sex should be downgraded to mere acquaintances.

Don’t jeopardize your spouse's trust
by being alone with someone of the opposite sex without your spouse’s knowledge and approval, even if you think it’s an innocent meeting or lunch date.
"And the two will become
one flesh. So they are no longer two, but one flesh." Mark 10:8