Self interest is not always a conscious thing and the line especially blurs when the primitive mind makes an autonomous decision without first consulting the rest of the brain.
I completely respect that you choose X2 over X1. I accept that you love them differently and when it comes down to it, you would rather be with X2.
Still, I challenge you to make amends with both. You may not ever get back with X2. You may want to ONLY focus on trying to R with X2.
Are you prepared to rebuild your relationship with both X1 and X2?