firstly, never let anyone tell you how to grieve. Of course you are sad, and confused by that sadness, because despite how logical and right our decisions are, for a lot of us our hormones and drives are keyed to giving life.
You did make the right decision, but you still need that space and support and love that anyone who makes a hard decision needs.
I don't think society is very gifted in supporting pregnancy loss in any form. We have expectations placed on us to just get over it. You and I and many woman know it just isn't that easy.