For me my hardest decision I've made is loving someone that is not the same with my religion. I know that he's not the right one for me but here I'am still loving him without any assurance that we can be together till the end.
The hardest decision I have ever made is when I sell my house and move home, going from one area to another because we are in a new place, like a number starting from 0. (Having to find a new job, creating a new home and so on) and the hardest thing is now buying the land, I lack $ 8000 which is the hardest thing in my life, have to earn money to pay for shortfall with short time.