We all misrepresent the event of coming out. Things like the It Gets Better Project kind of set up the notion that it even is a single event, some kind of watershed. While it's true that the first time you come out is usually the hardest, and it's the most significant, involving the people closest to you — coming out is something that you will do every day once you've taken that first step.
Quite often the first time is the only time you are likely to exercise any reliable control over the way you come out. Once that proverbial cat has been released from the bag, like any other form of public information, it passes from person to person. Under the best circumstances the people around you will just be honest about your sexuality and support you, respect your humanity and be sensitive to the ways in which your sexuality can have unexpected social consequences. This is great, but it means they're not generally going to avoid the subject or keep it quiet for you. They will (correctly) have a sense that deliberately avoiding the subject out of discomfort perpetuates negative behaviours. You'll be outed casually, and it's most often no big deal and when it is your friends are there and have your back (or they should if they're really your friends).
Not all circumstances are as innocuous. Office gossip, access to your social media profiles, and any number of things can out you to people who don't need to know your business or that might use that knowledge to cause trouble. Nobody whispers to a colleague that the new guy in the office is scandalously straight, so straight folks rarely consider that their willingness to discuss the details of your private life can, in unfortunate circumstances, put you at risk of harm; physical, social, or professional. It's not always clear when an essential truth of your life is something that another person or organisation is going to fail to deal with rationally and you will always have a sense of vigilance about who has been exposed to that knowledge and whether or not they will react negatively to it.
You'll come out every day for the rest of your life, and it won't always be easy, but it is important because the more we are part of everyone's daily experience the less of a big deal and the more a mundane part of life we will become.