Something I see a lot and I was guilty of as well, was how certain they are they can solve a problem.
Dev is sure they can solve it, then struggle for days.
I'm sure that given enough time they'll get it solved, but their struggle begins to make the team nervous and invites poor management to step in.
So, I give a TTH (Time-To-Help). Set a line, in minutes, where you work on a problem without making progress before you go ask someone for help.
Another one I see, similarly, is a confusion around information, knowledge, and experience. I meet lots of developers who read a blog post and claim they, "Know," some given topic. This is before they've applied it, tried it, worked with someone that has gone through it before. They'll develop a belief that they have the knowledge and experience behind it.
Getting a drivers license doesn't make you a good driver.
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