1) I thought I was going to always be fighting with the QA team, clients and designers, but the QA and designers are very skillful and respectful people so we never clashed. As for the client, I never speak to them since it's the Project manager's job and if I tell the PM that x feature would take too long or would be too difficult they would relay that info to the client.
2) I can't think of a specific thing, but there were many projects that were estimated at like a day or a week but ended up taking way longer than that due to unexpected behaviours or client changes.
EDIT: I had fears that I was not going to be good enough and was gonna fail miserably, but so far, so good
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