When two people get married and become one, on the biggest day of their lives, their wedding day, they don't lose their individual identity. Each individual is taking on new responsibilities, and is participating in a relationship, but they still have their own individual identity.
This is why I think boundaries can be a good thing. Boundaries comes in many forms. And we should have them. Not necessarily to limit ourselves, but to protect our personhood. Boundaries helps us to GUARD our HEART with DILIGENCE. We need to keep things that will nurture us, inside our mental state of mind, and the things that will harm us outside.
I think where boundaries can become confusing and problematic in a relationship, is in the element of personhood. The problem arises when one trespasses on the other spouse's personhood. When one crosses the line and try to control the feelings, the behavior, the attitude, the values and choices of their significant other. In my opinion, those are things only each individual can and should control. For a spouse to try and control those things, it violates the other spouse's boundaries and ultimately it becomes a major problem in their relationship. Our relationship with our spouse, or any other successful relationship is base on trust, and on freedom, to some extent. Feelings is one of the most important elements that promotes intimacy in a relationship. Each individual has to control their own feelings.
You can create good protective boundaries with your words. The basic boundary word is NO! When used directly it will let others know that you exist apart from them, and that you're in control of yourself. If you believe in GOD you've a spiritual boundary. Spiritual boundaries are just as real, but harder to see. Your personal boundary is your personhood. Your skin, and my skin, is the physical boundary of our body. Don't let anyone or anything breaks it! Don't accept mental or verbal abuse! Don't let anyone trespass on the BOUNDARIES of your personhood. Protect yourself at all times!