Cheer up - well, at least cheer up a little.
There will be some kind of renegotiation now because it is unavoidable. Britain is 'in Europe' whether it likes it or not: it's called History and Geography. There is no way out of either of them.
The renegotiation will eventually agree issues that could equally have been dealt with by staying in and fighting for them: democracy has always involved doing that. But Cameron chose to solve his internal Tory problems by referring them to 'the people', a cop out for party political ends, not for the sake of 'democracy', and certainly not for Britain's national interest. It's backfired disastrously for him and he has gone. That's justice.
The tragedy is all the pointless and avoidable waste and chaos meanwhile as we start solving the same problem over again. That's what people do, isn't it? We're a dopey and fragile lot.