I did. I'm thankful I did. I would have never had light at the end of the tunnel. About 25% of the population has an anxious attachment style, where this sort of behavior is expected when they are in an insecure relationship.

About 25% has an avoidant attachment style, who have a high likelihood of infidelity.

50% are secure. Secure types naturally help anxious types feel secure, so they don't do this shit. Avoidants actively make anxious styles feel much more insecure. As do anxious types on avoidants. Guess who gets a lot of consistent matches? Anxious and Avoidant. Secures don't stay in the single pool for long, neither do anxious. Avoidants are dating a long part of their life.

An individual can change their attachment style, but avoidants have the worst time doing so.

You can get a general sense of attachment style from the post.

1. If you could understand this from your partner, and see why they would do this, and would accept an apology, you're secure.
2. If you find that you see yourself doing this in certain situations and that it would be very relieving, you are probably anxious.
3. If this plain disgusted you, made you feel violated, or made you very angry, probably avoidant.

There are subtypes of course, and lots of other traits. One thing to note is that the last significant (albeit tiny) proportion is disorganized. They experience traights of anxious and avoidant, and typically have very unstable relationships.

Edit: Wow, a lot of y'all are missing what I'm saying. I never said it was healthy or good. I said it was an insecure relationship. As in the person doing the digging is ignoring other red flags that are causing their anxiety to get to this point.

Seeing the responses here I want to add something to make people more upset: Co-depenancy is a myth.