We all have bad days. Most of my days are bad. I completely understand being overwhelmed by that feeling that you are losing everything in your life that matters. We all feel your pain.
I dont think that you need to accept that he is never coming home. You might accept that it is POSSIBLE that he will not come home. The odds are in your favor here though just based on OW age. Im close to the same age as your H and I would not be able to deal with an 18 y/o for long. It might be alot of fun for sex for a minute but then all the dumb sh!t that a teenager has going on would creep in. Your dad is just trying to get you to detach. Hope your night gets better.
M:33 W:30 T:10 M:2 B/D: 5/27/14 S: 5/28/14 Wife moved back in 7/18/14