The thing about contractors (not just pools) is that everything is always sweet & clean at the showroom or when you are about to hire for a job. It's when the rubber meets the road you learn more of what's really important - timeliness, quality, professionalism. Even the best contractors out there are only as good as the employees they hire, and believe me, they get ALL kinds. They may be skilled, but they have personal issues and such that delay work schedules just as much as equipment, rain, etc.
I have typically found it best to keep good notes and a cool head. When the time presents itself to call or visit someone about your timeline or anything else, you'll definitely know deep-down it's time to express what's on your mind.
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In fairness, I should also say not all contractors are bad. Not at all. But I have just gotten to the point in my own personal experience where I am not surprised when this type of thing happens. I try not to let it overwhelm me or damage the relationship I have with the contractor. Deep breath.