Looking back on your career and experience with composites, please share some mistakes you made and what you learned from those mistakes.
This should be fun, sorta like an AA meeting…
I think the biggest mistake I’ve made so far is stubbornly using quick connectors for air lines and ball valves instead of proper line clamps for my infusion process. Ball valves (at least the harbor freight ones…) will always have some amount of leakage in them.
The problem with quick connectors is that based on their position (rotation, angle, etc), the amount of leaking will always be different. This means you’ll be pulling different amounts of vacuum during infusion if you end up moving the part around, which is a big no-no.
There are too man to list, but those two are the most important and I think are good to share since I’ve never seen anyone complain about them before 
Biggest mistakes I have made have been rushing and trying to take a short cut. eg: not getting everything ready beforehand, not waiting for resin to cure before sanding, cutting, painting, demoulding etc.
Biggest mistake in my career? Not becoming a doctor. Or a lawyer. Or a dentist. Or an engineer. Or…