In ancient times any important city was surrounded by a wall. If an enemy army came to attack, then the inhabitants could simply shut the gates of the city and guard it from the walls. The enemy, of course, would then lay siege to the city: they would surround it with their army and not let anyone in or out. This was usually not too much of a problem for the people inside the city, for as long as they had food and water they could last for months. The water, of course, was especially important. After all, you can go for several weeks without food but you can only go a few days without water.

In Bible times they would often get their water from a spring within the city or from a well. As long as this spring or well held up, the people under siege would be okay. But if the spring or well dried up, or if the enemy was somehow able to cut off or poison the source of the water, then the city could fall within days. That water was the very life of the city, and if anything went wrong with it the city itself would fall.

If we compared our lives to an ancient city, then the "wellspring" of our life would be our heart. If anything goes wrong with our heart – if we do not guard it from the enemy of our souls – then all is lost. Indeed, it is for this reason that the Lord gives us this command: "Guard your heart above all else, for it is the wellspring of life!" (Proverbs 4:23)

The enemy of our souls loves to attack our marriages. For this reason, it is important to consider what we need to guard our hearts against in the context of our marriage relationship.

Guarding your heart from a critical spirit

At the beginning of most relationships, husbands and wives find it easy to praise one another. In many relationships, however, these words of praise begin to dwindle and words of criticism begin to take their place. These words spring from a heart that has become critical, cynical, or perhaps unforgiving. The results for a marriage are lethal. "As charcoal to embers and as wood to fire, so is a quarrelsome man for kindling strife" (Proverbs 26:21). "A quarrelsome wife is like a constant dripping on a rainy day; restraining her is like restraining the wind or grasping oil with the hand" (Proverbs 27:15-16). Before long, we have completely torn down our spouse and alienated him or her from us.

What does guarding our heart look like here? It may involve such things as: repenting for hard-heartedness and unforgiveness; dwelling on the things about our spouse that we can be thankful for; expressing those things to our spouse verbally or in writing; asking a friend to pray that the Lord would soften our hearts and take away a critical spirit.

Guarding your heart from emotional adultery

Adultery comes in many shapes and sizes. One form of "adultery" that we often do not think about is "emotional adultery." This happens when another person of the opposite sex begins to take the emotional place of our spouse. The reasons for this are many. Sometimes it is because we feel an emotional distance from our spouse or a lack of connectedness. In order to have our emotional needs met, we then develop an emotional relationship with another person of the opposite sex. In other instances it is simply because we get along well with someone of the opposite sex and enjoy the attention and the feelings that come about when we spend time with them. In either instance, however, we are letting someone else of the opposite sex take a place in our lives that only our spouse should have.

The dangers here are very obvious, for emotional adultery can often lead very quickly to physical adultery. Guarding our heart from emotional adultery may involve such things as: repenting for flirting with another person and/or developing an unhealthy emotional attachment to a person of the opposite sex; confessing to another Christian what has happened and asking for their prayers and accountability; seeking counsel from a pastor or Christian counselor.