I have seen many people from my flight school failing airline assessments and they all have jobs somewhere else. Almost always better than the first offer. Call it destiny...
Don't underestimate a failed assessment though. it is very bad for you self confidence and you have to look back at the assessment carefully to see where you went wrong and how to improve on the next one. Ask for feedback if they can.
failing an assessment is a major bummer but keep your head up. If you are good enough another chance will come, at least in the current market.