Charlotte, that's what we're here for, truly. Who better to vent to than us? We can't possibly understand what you feel inside but we have this shared experience, which makes it easier for us to understand your feeling perhaps better than most.
The only bit of advice I can offer is that it's important to remember that HRT (constantly changing hormone levels) makes some of us more vulnerable to our fears and feelings, sometimes amplifying the peaks and the lows. To me, this means that when I'm feeling absolutely hopeless and desperate, I have to remind myself "oh, I almost forgot: I'm loaded with estradiol, and this existential dread and despair I'm feeling might not be as bad tomorrow. I have to try to step outside of my head a little on this one because I'm still coming to terms with a brain that works differently than before."