Before I tell you why I am feeling sad, I probably ought to tell you that I am an extremely pragmatic person, I do feel emotions, but I am very very able to "box" or "shelve" emotions and move on with my life without regret, or (touch wood) any form of mental health problems.
My dad died 4 months ago. He had been fighting cancer and although had been in remission he caught infection after infection, some of which left him severely disabled, one of which killed him. I miss him every day (of course) but am totally able to come to terms with his death, because until he ended up in hospital he had been an incredibly active man, and living a life, at best in a wheelchair, at worst bed bound, would have been sheer hell for him - and I think he would probably have taken his own life anyway - the thought of him making his loved ones care for him, wait on him and tend to him, would have been totally unbearable for him.
Since his death I have helped to look after my (still young) mum and my daughter. I have also fallen pregnant :)
DH has today had a huge argument with his father, over his (FIL's) drinking. FIL is only in his early 60's - in good health, except for his weight, though likes to "pretend" he is dying of different illnesses - reflux means he has oesophageal cancer 
, stomach ulcer means he has to undergo a huge operation (it doesnt) and might die to a (non-existent) heart problem - you get the picture.
I have managed, so far to avoid FIL and walk away when he tells me he is dying, because it is, at best, totally insensitive, and at worse, well, just downright rude! My dad died an incredibly dignified death, with hardly any complaints, moans or groans.
FIL was an alcoholic when I first met him, but managed, by himself, to stop drinking, and remained dry for the best part of about 6 years. Recently though he has started drinking again, small amounts at first, but now he starts drinking at about 4pm and "hides" spirits in his glass of wine :(
DH confronted him about it today, as it is breaking his heart that his dad is likely to drink himself to death. MIL is also wrried about this, but they have a very "traditional" man and wife relationship, so is not able to ask him to stop :(
DH is really worried, and almost in grieving for his father - rather like I was when my dad was in hospital and we were told he is unlikely to ever walk again, let alone survive the year.
I really really want to support DH, but whenever I think about the fucking injustice of it, I just want to cry. My dad would have done absolutely ANYTHING to still be here today with his family, whilst this man wastes his life and gloats about how ill he is becoming.
I know there is nothing anyone can do - i just feel so cheated - DH will want to, understandably, spend time with his dad whilst he still has sober periods, and is here with us - all I want to do is smash the stupid, selfish man's face in. DH feels the same as I do, but of course, the relationship is vastly different, because he loves FIL - it is his dad.
Thank you for reading - sorry it is so long.