Kantriakhor

What should a person do if he/she had once cheated on his/her significant other (not married)? Say it's about a year ago and the cheater has realized how wrong it was and has since fallen deeply in love with this significant other. Also, add in the fact that the significant other has once said that he/she would break the relationship off if the other (whom in this case is the unrevealed cheater) was to cheat on him/her. Should the cheater come clean, anyway, risking the relationship with the person he/she loves, or hold it in? Or any other suggestions as to what this person should do would be fantastic.

Yes, yes, and yes!

The one being cheated on has the right to make an informed decision about their relationship with full disclosure. Avoiding telling them in order to "spare them" or "spare the relationship" are little more than contrived excuses cowards have used to rationalize saving their skin.

It'll hurt, yes, but honesty is what matters, and down the road the one being cheated on will likely find out, only way to keep a secret is if only one person knows.

I doubt 75% is a realistic figure and would love to see all the leg-work for that statistic.