I have been working as Bioanalytical scientist and my biggest obstacle is things expiring and wasting my time on preparing solutions or reagents for samples I am suppose to extract. So far in my career I have learned to check solutions expiring dates every day before I leave work so I know what is expiring and what i need to make before my samples arrive. Because usually in CROs sample turnover are huge and quick. Big pharmas usually want their data next day so if things are not ready that waste so much time unnecessarily.