Dear, no need to give any sort of justifications. Justifications show weakness, helplessness & allow others to find a hidden culprit in you or to treat you mercifully.

Although, there is no justification for failure, but accepting one's failure with open heart could be the best possible alternative for justifications. Just say "I tried but could not make it" & then move on. Even those, who love you a lot and who might accept your justifications for the time being will surely ridicule you at any future failure, when you would have come out of this trauma. So just take the failure lightly & move on. That is the best defense mechanism.