Relationships, like people, all work very differently from one another. There are so many kinds of relationships with so many ways of, for lack of a better word, 'functioning'
Just to list off a few of those differing relationships to make my point, here goes: Committed heterosexual couples, committed homosexual couples, poly amorous persons, open relationships, open marriages and swingers.
People of all different walks of life have different desires, different needs emotionally, mentally, spiritually and sexually. Now, what works for one relationship may not work in another. While one couple may prefer to commit entirely to one another, another couple may decide to share their relationship with others.
I do my best not to judge. I would not ask anyone I wasn't dating to adhere to my relationship ideals, nor is anyone asking me to adhere to theirs.
What I will point out is that regardless of the relationship setting to any of these examples, they all tend to have a couple of things in common; Respect, honesty and communication.
Each person involved in any type of relationship will have certain wants and needs in the department of those three characteristics that they'll expect their partner(s) to adhere to. Whatever the rules and functions of that specific relationship, every party involved will want to discuss and come to agreements on if things are going to work.
Having made that point, there is one aspect of any of these that is never okay: Cheating.
My understanding of how open relationships of any sort function is that there is always honesty about what it happening with whom. There is a level of trust there because the lines of communication are kept open. Reaching a point where you're stepping outside of whatever boundaries have been drawn to the relationship is dishonest.
If you're committed emotionally and physically to anybody and you break that bond in any way, you're cheating.
I could sit here and point out that if you're in an open relationship that simply requires that you inform your partner before sleeping with someone else and you choose to engage in acts without communicating that to your partner, you're cheating.
I could point out that when you're committed to more than one person and you're stepping outside the lines with one or both of them to get your jollies, you're cheating.
I could point out that when you have commit yourself to one person in all ways and you decide to step out on them, you're cheating.
What is cheating? Well, for me, it's a complete lack of respect.
At one time, the person or persons you're dating/married to were what you wanted. Their desires were your desires. As anyone that has ever gone through a breakup or divorce will tell you, desires change. People change. What doesn't change, however, is how one should go about taking the next step when they're not happy anymore.
Leave. Leave first. When you realize things aren't running as smoothly and they are not things that can be fixed, take the steps. When you realize the feelings you once felt are not what you feel now, move on. However, have respect.
As I said before, the person that doesn't fit your life anymore was the right piece for a time that is gone. That person once made you smile. They once made you laugh. They once made you feel like all you needed was them.
Respect that and remember it when the time comes to let go... because nothing tramples the good memories more than disgracing them by cheating. It's low-down. It's dirty and it's unfair to the amount of time that person put into you.
Now go forth, ladies and gentleman and think before you act.