It’s both noble and self-sacrificing to stay in a relationship because leaving would crush your partner. You’re loyal to the core, but also profoundly dissatisfied. Now your struggle is to balance the vow you made to your partner to stay in the relationship against the emotional drudgery and the desperate longing to be free.
If you are resigned to stay despite your own despair, you have a certain kind of resolve that keeps you in a relationship that has been unhappy for longer than it has been happy. You are exquisitely aware of the guilt, chaos, trauma, and judgment from others and self-disgust your decision to leave your partner would create. Could you live with yourself after leaving? The idea that it would just be too unbearable for your partner is the main reason you stay. But staying also feels unbearable. What to do?
Now, usually in a blog post, this is when an author might offer solutions for this incredibly excruciating and complex quandary. Do you consider leaving, because why spend your time miserable when you only live once? Wait, do you consider staying, because leaving would require sacrificing your reputation, disappointing people you love, and "abandoning ship" are not the legacy you want to leave behind? How you make this decision is an essential part of what makes you, you. One is not better than the other. They are just different ways of understanding yourself and treating yourself in the world.
So you see in this case the answer is really no answer at all. It's about acceptance of who you are. All I’m going to say is that you are in an understandable position and that your dilemma is excruciating. And the fact you even have this dilemma is noble, and if being noble provides you with a sense of self-pride, and helps you keep balanced, then there is an equally profound value to staying the course in your relationship. It is not a resignation, but a choice. Your steadfastness is honorable.
Now, if you have elected to take the other path and leave, please understand it’s human to put your own needs first. Humans are wired to avoid loss—psychologists call this loss aversion—and so your ability to leave depends on being able to visualize a better path for both you and your partner.
No matter your decision to stay or go, be as aware and deliberate as you can. Try to work on making it better life for yourself, rather than letting it make you. If you’re willing to resign your "pursuit of happiness" to give that same gift to your partner, do it with intention. It is a choice not a resignation. Working towards accepting your decision as fully as you can will aid in not looking back with regret. Acceptance of your decision to remain can even create a little more lightness in your relationship, because it is your conscious and empowered choice.
No one can tell you whether to stay or to go. No one has your perspective. And no one can know how leaving would balance the pursuit of happiness against the guilt, shame, and altruism of keeping your long-term promise to your partner. It's a terribly difficult decision to have to make for yourself. But know that inside or outside the relationship—whether you elect to stay or go—it is okay to want fulfillment in your one time around in is world. Amidst the guilt of breakup or choice to stay in your unhappy relationship, the responsibility to be you is up to you.