I wish I knew that this guy you left me for was actually worth it to you... and was better for you than I could have ever hoped to be... and I wish I knew he treats you wonderfully and will forever make you happy.
If I knew this, I would be able to be thrilled for you. Instead I worry you left me for something that was simply more "convenient" and are trying to convince yourself that he's perfect for you.
If you had left me for someone who was truly better than me, then I could feel better about your reasons for leaving me.