Rarely do we have all the facts. We work based on the evidence available at the time, and even then some things may be overlooked.
Consider Alice and Bob. Alice asks Bob for assistance. Bob snaps at her to do her own work and quit bothering him. If Alice does not know Bob well, she might conclude that he's a jerk. If Alice knows that Bob has gotten very little sleep for the last few days and that he has a major deadline approaching, she might conclude that he's stressed out. Without changing the facts, just changing their availability to Alice, it is clear that her conclusion may change.
This is how scientific discovery works. The available facts change all the time, and so our conclusions change. New methods of measurement, new datasets, knowledge crossing disciplines, any of these things can potentially change the conclusions we draw. Often the differences are subtle. Still, if you are in the mindset that conclusions are fixed Truths, finding that you're wrong (again and again and again) can be disconcerting.
At the same time, we can't wait for all the facts before making any conclusions. You may never get all the facts. You'll be stuck in inaction, indecisive as Hamlet.
This is what I struggle with now. Do I have enough facts for a reasonably firm conclusion? Which facts can I collect – which experiments can I run – in the near future that would help? As fun as it may sound, I can't explore forever. It's not a realistic prospect. I need to gather the information available to me now and conclude what I can. Tomorrow's new facts may tell me I am wrong, but I won't know until then.