Just one bad hour and you named the whole day as a worst day. May be you were not good at that particular hour, may be the efforts you were putting in that particular hour was not sufficient and most important hour. May be that thing wasn’t meant for you.
Everything in this works works on a plan. No! I’m nit talking about your plan. There is one planner of every creature on this Earth. We are his child and we have to keep faith on his plan. All we need to be is patient. Patience is actually the MANTRA for good life. Having failure is OK. But accepting that failure as a lifetime failure is not good. You have to keep patience. Things will fall on your space. Think of the time when you achieved success. Think of the time when things were going good.
Blaming the situation or blaming your own capacity is not good will not help you. All it will do is pull your morale down. It will create feeling of self doubt in you. Always keep in mind that nothing is temporary, the time which has shown you the failure will also pass on. You have to decide how you deal with that failure. Every failure comes with a lesson.
If you accept your job interview failure with a positive attitude and thought to be patient and work harder on the next round, CONGRATULAION!! You passed the exam of your life.
And always remember passing every exam of life is more important than any other exams of your life.