I ended up having real difficulty with anxiety at work - was frequently leaving my desk to camp out in the loo for a time while I had a meltdown/panic attack. I was also dissociating at my desk and in meetings a lot, though I didn't realise that at the time.
For me, the most difficult thing was the office environment - it was all open plan, lots of people all sitting close to each other around 'pod' desks, all meeting rooms had glass walls...there was literally no where to get any privacy and I felt so exposed.
But I really liked my job and the people I worked with.
I ended up having a massive panic attack and walking out of work one morning - ended up having three months off, during which time my symptoms went off the scale and I was diagnosed with PTSD.
I'd spoken to my boss about feeling anxious and she was very supportive. But, we were good friends, so it was a different relationship to me just telling HR/management who I only had a strictly work/non-personal relationship with. In fact, she was so supportive that work paid for my therapy. And, in fact, they're still paying for it as I got made redundant at the start of this year and I managed to negotiate more therapy as part of my redundancy package.
When I look back on it now, although I knew at the time that I was feeling anxious, I don't think I realised just how bad a state I was in. I can see now that I was in a constant state of fight/flight, that I was having numerous panic attacks, that I was missing hours in a day sometimes by dissociating. And that, as well as feeling bad, my performance at work was awful - I was avoiding meetings, not being productive, couldn't concentrate, was so forgetful, was missing things through not being present... So, looking back, it was an even bigger shitstorm than I was aware of at the time - and it did feel pretty horrendous at the time! But I was good at hiding it too - I think to most people I looked ok.