Hi, I'm new here too...and also the spouse of a D. I had to respond because NO YOU ARE NOT A HORRIBLE PERSON.

Living with a D is very difficult. Like you mentioned, not everyone is cut out for it.

If you truly feel like you cannot take any more, then leaving may be your only option.

What you have to question is this...
1. Is leaving the marriage going to be easier/better/happier for me?
2. If he got better, would I feel differently?
3. Have I done everything I can to make this work?
4. Do I love him?

After you have given those questions deep thought, then make a decision.