That doesn't mean in most cases you shouldn't engage a couples counselor to assist in 'sorting-out' things between you. When the marriage or relationship is no longer a priority; when there is lack of attention and energy given to the relationship; when sex is viewed as drudgery or a chore, it is certainly time to seek the assistance of a qualified couples therapist. Know why you want to end the relationship. Know that there just wasn't any other solution. Know the factors involved. Know that there just isn't any hope for it.
But, if you must break up, do it with dignity and kindness. There's no need to say painful words. Be respectful. Be mature.
Ideally, you will want to provide support to your partners so that (s)he doesn't feel dumped-on. Go to a coffee shop or a community park picnic table so that voices will be kept at a respectable level. Try to understand where your partner is coming from, instead of feeling personally attacked. Explain why you no longer have the feelings you once had. Allow your partner to speak, and, listen carefully.
If you can't do this on your own, see someone who will help you through the process. It can be the same person who you saw for counseling. Most of all, KNOW that a relationship is not a prison sentence. If it's not joyful, fun, harmonious, respectful; then, think about the very best you can do for both of you.