Even if your clumsiness is a great vice that is so great as to be near sinful, you would not consider this to be an injustice, because you can't really be unjust to yourself. However, if a co-worker purposely causes you to spill coffee on your tie, you know doubt would cry foul. Justice is involved specifically in our dealings with other people.
Justice is a matter of equality, but equality can only be judged if there is more than one person.