I might be heading for a divorce [sorry if TMI, but you [we?] all are a great community of friends here so I thought I would share]. Been together for 15 years. Any advice to get the marriage back on track? 
First, that's never happy news and you have my complete support - no adverse opinions on car commentary for the next little while!
Hard to give advice not knowing the context.
I agree to a degree - share only what you feel comfortable, but a little context will certainly help us give advice. In Ron's previous case of ploughing a personal trainer, the focus would have been based on Ron's feelings (whether he can accept that or whether it's an immediate termination of the relationship). In a case of a couple running out of steam, usually there's some sort of complaint that leads to the deterioration (whether it's an issue of intimacy, bad habits, etc).
I've been married for <2 years (together for 9 years total though). I do not pretend to be an expert here, but my wife has so much to offer, which came at the price of her having high expectations/demands of me earlier on in our relationship. We were on the verge of breaking up what seemed like monthly (it might actually have been) in our first 2-3 years together, but since then I've taken her criticisms constructively, made myself a better person, and we're so much stronger for it.
It's not necessarily that you've done something wrong, nor that she has...but sometimes people change their wants/needs and expect their counterpart to just simply "keep up" (oftentimes without notice).
My opinion may be unpopular, but I am 100% AGAINST
formal counselling. While much of what I do is mediation with a neutral third party at work, I find that the thought of "needing" counselling often forms resentment for the process. Ultimately, that may limit the potential for success.
My recommendation is to have an open, level (NON-HEATED) discussion where you two work together to find the root of the problem. If it's something that can be fixed, even if it takes a long time and a lot of work, absolutely you have a duty to each other to try that route before calling it quits. The important thing is to be cognizant of emotional intelligence - this is not about
blame; rather, it's an attempt to repair. Avoid using the word "but", try to focus on the positives, and accept that you have some responsibility in everything. Show a willingness to work together and change gradually over time. Don't proclaim, "I CAN CHANGE!", but accept that there are subtleties than can be effected to produce the outcome desired.
For example, my wife originally was the type to say, "it's fine". Clearly, she didn't mean "it's fine"; rather, she meant "I don't like this and I expect you to know that!" It took years for me to pick up on her clues, but in those years, I blamed her for not communicating with me effectively. She was doing the best she knew how to, and over time she opened up to me and now probably tells me things too bluntly
, and I can look at her face and know when she's happy/unhappy.
If we called it quits, my life would be different. Easier, perhaps...but not as rewarding. You're 15 years in - you know what each other are like, you know the pros/cons of each other. But you're not the same kids you were when you started dating, and life changes can have effects on the way we interact with our significant others.
I wish you the best of luck and offer my continued support throughout. Let me know (PM or otherwise) if you have any questions/thoughts/etc.
