As a Biblical Counselor I am frequently faced by people with relationship problems. They receive help with the immediate issue, and then are taught the marks of a healthy relationship.
The most important aspect of a healthy relationship is trust. The ability to trust your friend, boyfriend or husband is the single most important thing on which all the rest hinges. Trust and confidence that you are not being lied to or deceived in any other way is the bedrock foundation for a successful relationship. If trust is violated it can and must be earned back over time for the relationship to continue.
Here are some ways trust is critical to a healthy relationship:
You have to be able to speak freely to one another. There must be confidence that you can truly say what is on your mind and in your heart. This is not an invitation to be cruel or hurtful, but helpful and constructive with the goal of helping each other to be more like Christ.
Some things are simply hard to hear (wounds of a faithful friend) but are needful. In fact, a health relationship will at times be conflictual for that very reason! Our flesh does not like to be confronted or put down by other people but there are times it is simply necessary to be told difficult things.
In a healthy relationship there is freedom and trust to have verbal intimacy. You will talk things out rather than clamming up and bottling your thoughts inside of you even in conflictual situations. There is a confidence level that allows for risk taking in conversations.
There is a willingness to confront each other about sin. There is openness in loving confrontation of sinful actions and attitudes and a right and God-honoring response to their correction.
These things reveal that you have each others best interests at heart.
(look not only to your own interests,Phil 2)
(rebuke one another)
People in healthy relationships willingly put the needs and wants of the other person ahead of their own. You consider them better than yourself (Phil2) and are willing to sacrifice for them. In essence, you are their biggest "fan" and their loudest cheerleader. This is done without bitterness, rancor, or arguement.
Healthy relationships allow for other friendships and relationships to form. While in a marriage it is not wise to develop exclusive relationships with the opposite sex but it is very good for women to have female friends and men to have other men to hang out with. In other words, a healthy relationship is not suffocating. I have observed situations where men do not allow their wives or girlfriends to go out without them, or demand moment by moment updates as to where they are, and what they are doing. This is indicative of a lack of trust and means there is more going on here than is meeting the naked eye.
Healthy relationships allow for honesty in financial matters. It is always concerning to me to see credit card bills for a women arriving at the office, or the neighbors house instead of her own home address. This is sneaky and deceptive and reveals there are some serious problems in the relationship. There should not be sneaky purchases, or spending money on the sly. Budget money should not be secretly spent on purchases that have not been discussed with your spouse- ever.
Two people in a healthy relationship will enjoy each other's company. There will be plenty of laughter and fun but there will also be times of companionable silence. This is true for friendships and marriage. Each of us will be very fortunate to have one or two good relationships like this in our lifetime. If you are married, one of these good relationships had better be with your husband and that one should be permanent!