Is the Christian couple allowed to separate? Well, let's take a look at I Corinthians chapter 7.
For two Christians who are married to each other, the purpose of separation is reconciliation. It provides an opportunity to break from the situation, each pray and consult with God, and then come together to rebuild their relationship. It's a tool for healing.
Paul cautioned that she is to remain unmarried (in this instance he is speaking as if it were the wife who left) and not seek another releationship. At best she would eventually be reconciled to her husband. Because of this, the husband is to leave room for reconcililation and not simply divorce his wife and move on.
As Christians, our goal as we grow in Christ is transformation. And if we are striving to walk in love with our own brothers and sisters in Christ, how much more so should we work to do so with our husband or wife? As the fruit of the Spirit develops within us (love, joy, peace, longsuffering, gentleness, meekness...),surely it would help toward improving our relationship with our spouse.
It's important, however, that both agree with this strategy. Often the couple may indicate their preference to heal the relationship and remain married. By setting a time limit for the separation, they can work together to meet that deadline. Without a plan, however, it is likely they will just drift apart and eventually divorce.
I know that if the situation is tense enough for you to be thinking about divorce, then the break a separation provides can feel like a release. And it can feel so good! You start imagining a whole life without them instead of a closer walk with them.
When things are emotionally unbearable it may actually be helpful for both of you to step back, take a deep breath, and reassess your problems with an eye toward fixing them and returning into fellowship. If you can be in agreement on this, draw closer to God as you try to work things out. And may God be with you.