If you have lost one job, so what?! A million other jobs are there in the world. You can take another one. Never mind if you get paid a little bit less in this job and you got more there, move on!
Life is worth much more than sitting and brooding and wasting your energy and your time on what has happened in the past. It might have been because of your own mistakes in the present or it could be that you were unable to see your mistake in the past. That could be because of a past life, but never mind. There is no point in analyzing the past now. We need to look forward and just move on.
Don’t lose your enthusiasm for whatsoever reason.