As the UK is demonstrating, it was always possible to leave simply by giving notice, and it's possible to negotiate a new arrangement.
The "I'm me" refers to the UK wanting its cake and eating it - by not meeting the EU half way in the trade relationship, of course the UK does not get the benefits either, but they assumed they would get similar benefits.
Sucks for those of us who live in the UK. We've basically lost a bunch of rights and privileges. For the individual person in the UK I would say we have less personal sovereignty now than we did before, just because there's less we are free to do with our lives than before. For UK businesses that trade with the EU - and this includes IT contractors - there are considerable barriers to trade now as well, which are causing customers in the EU to be increasing disinclined to bother with UK suppliers.
Much of the talk about the EU is about trade, but there were a lot of personal freedoms enshrined in the EU treaty granted to all EU member citizens as a condition of membership as well, which we UK citizens have now lost. For many of us it's a severe and painful loss. You can probably tell, I care much less about the trade, and much more about what personal rights and freedoms individuals (and families etc) have to be free to enjoy their lives.
I think individual persons have been harmed by Brexit much more than a "global elite", who can manage their assets just fine and aren't really affected.
Y'know what we call countries who think their right to self-determination overrides others? We call them paraiahs, or war criminals if they really push the issue.
Pretty much every sticking point of the UK/EU negotiations boiled down this. And the stated reasoning was an "I'm Me" argument. The UK deserved sovereignty because I'm me. The UK deserved market access because I'm me. The UK should not lose access to their cake just because they ate it because I'm me. The UK deserved no border in the Irish sea and no border in Ireland because I'm me. Absolutely no effort was spent on meeting the EU halfway or, at the very least, trying to adopt a negotiating position that was not immediately poked full of holes by random Internet commenters.
And, for what it's worth... the UK never intended to leave the EU at all. Brexit was a sham vote intended to go the same way as the Scottish independence referendum. When it blew up in David Cameron's face he basically jumped ship and handed UKIP the keys to the country.
This is the problem with antiglobalism: it has yet to suggest a viable alternative to the thing it is fighting. Putting up borders and trade barriers everywhere means rolling back everyone's living standards to the 1970s; but it does not matter because the antiglobalists would become richer in the process. In a sense, the UK's negotiating position was less "we want market access and a trade deal" and more "we want you to unconditionally surrender and join the new British Empire".