When I hear you talking about your mixed emotions about shutting down your tank, I couldn't help but think about pre-breakup thoughts, especially in a long term relationship. Feelings of being stuck, resenting and procrastinating some basic interactions, guilt and sorrow at even contemplating leaving, etc.. Ideally you should love what you do with your time. People rarely get to have that with work, but our personal relationships and our hobbies can and should be uplifting and supportive not a source of angst and a drain on our emotions and our energy.
If we were talking about a relationship, you would have been dating a guy for 3 years but considering breaking up for more than a year. It can be hard to break up, especially if the other party is not a jerk. They've done nothing wrong, nothing much has changed, but you just aren't feeling it like you used to. Well all the new outfits, weekend getaways, special dinners, and whatever else you can think of to rekindle the flame aren't likely to fix it. Sometimes the best for both parties is a clean break, even if it is very painful in the short run.
The good news is we aren't talking about another human, we are talking about a hobby. You can chose to shut down your tank and put it in storage and see if you get the urge to restart. If that hasn't happened in a year or 2, then you can sell off everything and move on. But don't keep throwing time and money at something that is adding stress to your life. Much as it can feel like it at times, keeping saltwater aquaria is not a religion, a way of life, a marriage - it is a hobby. Don't make it more (or less) than it is. As one human to another, I want for you to be happy. If keeping your tank can make you happy, great! If not, stop it and find something that does.
- Ian