"Very early on in my career, I accidentally mixed up two samples. I continued with my testing as usual and the results were way off. The entire team spent a lot of time trying to figure out why the results were so far off from what we expected and it took a lot of time. I ended up realizing it a day or two later when I ended up getting conflicting results from another batch of tests. The mistake caused a lot of time to be wasted and ended up resulting in rework. I was so hard on myself about it for a while. I was able to learn from my mistake and I always label and keep my samples separated now."