Very interesting a valuable question you have asked.
This is something both myself and my wife have struggled in the past.
In an attempt to keep this short, all I would suggest is thinking about it the same way you might when visiting different locations in the physical world, and how you adjust your approach there and yet still maintain a sense of self. For example, a library, a government building, a friends house, a pub, public transport, the mountains etc. These all allow a new sense of self to be practiced and explored, and obviously any online version is just as real as these examples, it's just a partial digital method of engagement. The feelings and interactions are just as real, it's just the social signals differ slightly as they might in any given context.
One main obstacle is what you post online, is potentially there to stay, and exist beyond your influence. Unlike a physical interaction, bar recording everything you do, it tends to have an engagement that we are only partially invited to. We miss things as conversation about us might continue, or opinions are shared without our presence, and are only reported back with moderation. The online version of this is we can dip into and out of that conversation, repeatably, and at any point in history. Essentially its timeline is different to physical, it's broken up in sections as apposed to linear.
I guess what I am trying to say is, moderating yourself at first seems increased compared to physical world, but after a short amount of time, it becomes apparent that it's a valuable experience to have and learn from, which really comes from finding your own path in engagement online, just like you would in the physical world. I have found this happens rather naturally, through just trial and error, much like life in general.
Basically, "be online", much in the same way as you would pick out your clothes, your favourite band t-shirt, how you decide what cafe or restaurant is for you. Shape your world as you wish it to be shaped, it's yours after all.
Someone said to be once after I commented on his shoes being incredible and I could never pull that style off, he turned and said to me so effortlessly, "sure you can, you just put them on".