@turquoise-- I'm going through the same thing as your dad. I think the emotional and psychological recovery from a heart attack takes longer than the physical recovery.
I've been having a lot of anxiety post my heart attack. When I experience chest pain, arm pain or breathlessness, I can't help but think that it's another heart attack. I'm actually on anti-anxiety medications now because of this fear.
I also had to quit smoking and make some major lifestyle changes and I think all of this is bringing on a mild depression.