Pride, stubbornness. not wanting to admit you were wrong. and of course it eats at you.
We often find it hard to say sorry to the person we hurt because we cannot forgive ourselves for hurting them in the first place. Or it could be ego stands in the way of you peering into your heart hence remorse is a distant, distant marker from where one is located.
TheLoneWolf and CitizenSmith put together is the perfect answer.
The appologising isn't difficult, accepting you did something wrong is :)
self-esteem & 100% agree with TheLoneWolf1986 !
becuz of feeling of shame to face him :'(