Speaking of this "one flesh" concept, in becoming one flesh, a man and woman become vital organs to one another. It should be looked at as though your very lives depend on one another. This is what God intended for marriage to be. It's in His Word. Also, in becoming one, you can't necessarily go anywhere without taking your spouse with you, that's if the love is 100. We've allowed marriage to be so defiled and diluted in our world society that there is no true respect for it. Wedding rings make some folks targets of malignant tumors of people who would come against the body of a marriage, to sicken it, weaken it, and eventually kill it; but only if allowed. Remember my post, "Chapters & Doggie Paddlers"? After marriage or at the point of committing yourself to another, certain chapters SHOULD be closed, and there will always be potential dangers doggy paddling around your yacht of marriage. Life lines should never be thrown to them, no matter how cool they are or used to be, no matter the memories shared in the past, and no matter the relationship that once existed. If a person's presence in your life or intent for you causes ill to your relationship with your spouse, then treat him/he like that loaf of bread which is on "the turn" and trash it.
Back to "forsaking all others": I think that forsaking all others has more to do with trusting God, than we may initially think. The first thought for many of us is that it simply means to put our spouses above all others, choosing him/her over mom and dad, or kicking all friends to the curb for this person. I think it's more about God telling us to be committed to one another, making one another priority, and moving forward with the life that HE has mapped out. But He also asks us to trust HIM to take care of all others who might have been priority before, and all of those we love and care for. The following may not be the best example, but I think it's relevant in the area of trusting God.
In January of 2010, I began praying for direction concerning my marriage. It was a turbulent one, and honestly, toxic one. It was not until April that I woke up from a vision of my kids and I standing on a clear horizon, just us, and happy. I was overcome with a sure peace of mind and of heart. I thanked God and asked that He bring my kids home to me, knowing I'd have to be willing to give them up in order to end our terminal disease of a marriage. This peace came to me on a Tuesday. It was the following Sunday when I went to my wife and told her I wanted a divorce and that our lives would be better without each other. I advised her that she could have primary custody and I could have the kids on the weekends, and we'd work out all the other details. Things didn't quite work out the way I was prepared to go. Like Isaac being given back to Abraham, Taylor and Davyd were given back to me, without my ever having to let them go. I thanked and praised God for keeping my children with me.
Trusting God is key to all. God will never steer you wrong. When a man leaves his mother and father to cling to his wife, he is simply trusting God to take care of those who can no longer sit at #1 on his priority list. Family and friends are not totally removed, unless those relationship pose threat to the marriage.
Many of us find ourselves struggling to do what it is God would have us do, simply because of our worry about family and friendships we think will suffer from our obedience. This is normal. Paul even talks a bit about it in 1 Corinthians, chapter 7: "But I want you to be without care. He who is unmarried cares for the things of the Lord—how he may please the Lord. But he who is married cares about the things of the world—how he may please his wife." This is not meant to speak ill of being married. It's simply a human reality. When you have a spouse, and kids in some cases, you have more on your plate than would a person who has no wife or husband. Time and attention is divided into more slices, but we have to make certain that God still gets the big piece of chicken.
In truth, giving your all to God is not necessarily forsaking all others. Giving your heart to God makes you better able and capable of taking care of all those you love. Placing God first in your marriage will lead you into oneness and a love that benefits all, including the would be forsaken. Getting your priorities in order is what it's all about.