A bar is a small workplace with a long memory
Ten to thirty people, working in close physical proximity, under time pressure, at night, often for years. Reputations form in days and travel between venues, because the industry in any given city is smaller than it looks and everybody has worked with everybody.
Being good at the job is roughly half of keeping it. The other half is this lesson.
Who everyone is
Barbacks. Your ice, your glassware, your restock. Be extremely good to your barback. They make your night possible, they are frequently asked what they think of you, and in a lot of houses they are the next bartender. Tip them properly, thank them by name, and help them break down at close instead of leaving when the guests do.
Servers. They take drink orders to your bar and their income depends on how fast you make them. A bartender who deprioritises server tickets in favour of the guests they can see is the most common source of floor conflict in any restaurant. Do not do it. Their tickets are real orders from real tables who are also waiting.