Many couples struggle with the temptation to pursue outside interests, either together or individually, and while it is a successful option for some, it can result in devastating effects for others.

When you and your partner committed to each other six years ago, what was the goal? If you are like most couples, there isn't a conscious goal and there is no stated understanding about why you are even together, where you're headed, or how you plan to get there.

I often ask couples with whom I work, "What is a good reason for you two to be together?" Probably the most common answer is "companionship," or "Because we love each other." The problem with these goals is that through the course of our relationships most of us go through spells where we are not particularly excited about the companionship of our partner - and can, at times, find others more interesting, more enjoyable, more fun, more whatever.

Therefore, if the goal is companionship, or the ever vague "Because we love each other," when the tides change and we temporarily lose interest in his or her companionship, or we temporarily stop feeling the love - we're likely to begin looking for a trade-in. Pleasure feeds off of novelty.

Research shows, for example, that when you get an ice cream cone, the first bite is the best, the second is still pleasurable, and beyond the third bite it's just calories. We like new and different. This part of our body chemistry is not particularly relationship-friendly in that we are frequently tempted by the novelty of another (and usually it is because we don't know them that they are so appealing!!).

Long-term-anything loses novelty - unless you work at keeping the pleasure there. Adding another into the mix is a "quick fix" - and one that may prove to be very damaging to the integrity of your bond, as you already seem to be experiencing.

Relationships take a lot of work to develop. They must be maintained. And there needs to be a common goal or purpose for your being together to pull you into the future together. Some have shared hobbies, shared political beliefs/passions, shared pets, shared children. It's important to have something about which you both care that is outside of your relationship - pulling you into the future, together.

In my opinion, the best reason for two people to partner is to support and encourage one another in being their best self, and live the life that is truest to who he or she is. This, by the way, can be very boring. Healthy relationships, as it turns out, are a bit boring.

In relationships we love to feel "known" and "understood." The benefit of this sometimes boring-healthy relationship path is that growing old with someone gives us the best shot at this - allowing someone to really begin to know us over the span of our lives. We want to feel like our partner "gets" us. We want to feel safe and secure and believe that no matter what happens, my partner is in my corner and wants what's best for me, for her/him, and for us. This is the benefit of enduring relationships, be they family relationships, friendships, or life-partnerships.

When you consider what is going on with you now, is it possible that allowing your partner to pursue this outside interest is going to help her become a better person, or somehow add to you and your relationship in a way that is meaningful and good? If you can't come up with a "yes" to this, then I suggest you stand true to what you believe and hold the line. If you believe this can be good for you, your partner, and your relationship, then by all means tell her to "go for it."

Just know that you may not be able to prevent your partner from making a decision she might regret, but you absolutely can prevent yourself from agreeing to something you will regret. Be true to your truth.