It's not absolute, it just that being on any form of HRT slightly increases your risk of thrombosis.
I was on HRT for about 7 years, having felt truly dreadful when my menopause began. My own experience is that it is the fluctuation in hormones that is upsetting, and that once my hormones settled, I was actually OK.
I decided to stop the HRT before surgery. I was offered the option of continuing, but being given post-op heparin. My personal view was that it was ridiculous to be taking 2 lots of medication (not saying what others should do, just what I felt). I also decided that I was miserable in the run-up to the op so I'd do 2 lots of misery together!
I drank lots of water and ate lots of fruit & veg. I didn't deny myself anything that I fancied and I scheduled little treats to make me feel good. I took a break from stuff that was causing me stress.
It took about 6-8 weeks for my body to get used to being without HRT, and from then on I have had no hormonal problems an feel quite well (apart from arthritis).
Not everyone will have the same experience, but wanted to share.