People always talk about bad luck when the last game of a big parlay loses, but in fact, it was super lucky to even get to that point - but I feel your pain 
I don't play such big parlays, but had good winnings taken away from me with late goals or some other crazy stuff. I am sure I also had a lot of things going my way, but you forget those ones more easily.
I think we all know these "crazy stuff" situations only too well. I remember once in the 90th minute I had already left the stadium, completely disappointed because my bet didn't work out and I didn't want to be stuck in traffic and then had to hear on the radio that "my" team scored 2 goals and I won my bet. I don't play such big parlays, but had good winnings taken away from me with late goals or some other crazy stuff. I am sure I also had a lot of things going my way, but you forget those ones more easily.Such situations you don't forget for a lifetime I think