The dictionary defines a friend as a close or intimate acquirement, well-wisher or supporter. We make friends in school, places of work and worship, social gatherings etc. Some friends we out grow, some we lose contact with, some become close rivals and sworn enemies while there are the few that the bible reflects to as friends that sticks closer than a brother. While you have the liberty to choose, limit and dump friends at will when single, the whole dynamics changes when married.
Getting married to a friend that you share the same friends with suggests that there is the greater probability of you keeping your friends when married otherwise you would lose some of them after a while. If you have bosom friends you would like to keep when married, it is advisable for you to introduce them to your intended spouse during the dating period and let the friendship ensue. However, be rest assured that the dynamics of your relationships with your friends would change when you say 'I do', especially if they are of the opposite sex and single.
After you've said 'I do', your loyalty, priority and devotion switches to your spouse. Everyone and everything else takes a subordinate position. If you spouse does not like or enjoy the company of any of your friends, get rid of them fast. It's hard but it may save your marriage. It is very true for the woman because she can smell gold-diggers miles away by her innate intuition.
As a couple you should desire to establish new friendship together especially with other couples that would be role models and able to provide support and encouragement. What happens to your old friends then? Marriage does establish limits on your involvements with them especially if they are still single. You can not have your usual girl's or guy's night outs without the express consent of your spouse. You would be looking for big trouble by keeping close relationships with friends of the opposite sex. You would be establishing a mine field and breeding ground for jealously and distrust.
It does not mean mean you can not have a friend or college of the opposite sex who you relate with from time to time. If they are worth your time and effort the courteous thing to do is to introduce them to your spouse. If they are not comfortable speaking with your spouse, it is an alarm bell. The reality of friendships in marriage is that you can not live as a single person anymore. The two are now one. No individual in the marriage has the sole decision to establish friendships at the expense of the other. You should not have any friend your spouse is unaware of, that is if you have nothing to hide.
A more sensitive situation is maintaining relationships with ex-boyfriends, lovers or husbands especially if there is a kid involved. The relationship must be clearly defined and boundaries established with the consent of your current spouse. If there is not any child or common interests between you and your ex, my advice it to dissolve any relationship in whatever form that ever existed. You must find the strength to do it if you want your marriage to be void of suspicions and doubts. Exs have a way to getting back together at the expense of the established marriage. Flee every appearance of evil and be the man or The Woman after God's Heart ! Every wise woman builds her house: but the foolish plucks it down with her hands.
Life does naturally dictate our friends. You make friends with people you share common interests with. You most likely would make friends with folks in church if you attend church activities regularly. The same applies to sports activities, places of work and schools. When you start having kids, there is the probability that you would develop friendships with other parents as well the same applies when you are pregnant. Your single friends gradually become insignificant and if they do not get married soon they fade away. Birds of the same feather do flock together.
All said and done, you spouse should be your best friend but not your only best friend. You should also have at least a very close friend (of the same sex) who you can talk to, share things with and who can tell you the truth and rebuke you when you err. Your spouse should know who he or she is although. Friends like that are rare to find, but when you find them they would be an incentive blessing to your home.