Should a healthy relationship with future potential be ended after a year of effort if you decided you don’t want a relationship anymore?

A “healthy” relationship stops being one the moment one or more of the involved parties decides to end it. Ethical relationships (that aren’t parenting of minor children that can’t care for themselves) only work via consent. The second that consent is withdrawn, the person choosing to ignore that key missing ingredient is engaged in an unhealthy interaction.  The future potential now exists with other people not currently involved in this scenario.

I guess what you’re asking is “Does this seem fair to the person who had no inkling they’re about to be broken up with?” It might not feel good (and it probably won’t), but it’s better they know they can’t get what they want with you and seek it elsewhere (just like it’s better you know you can’t get what you want with them and seek it elsewhere). Breaking up won’t be a pleasant process for either one of you. However, it’s absolutely necessary that you don’t draw this out.

If you’ve decided to enjoy life, work and freedom without being partnered, maybe one-night stands / friends with benefits / sex buddies / celibacy are more your speed (right now or as your inherent preference). Just let anyone getting involved with you know up front not to expect a long-term monogamous/partnered arrangement. I’m not going to chastise you for having a “fear of commitment” or some such thing simply because adults get to choose what it is they want to commit to. You’ve chosen to commit to unpartnered independence. There are people out there that want the same thing you do. If they’re amenable, seek them out and enjoy their company. If not, learn how to enjoy your own.