When I began HRT I was a little scared of breast growth. The reason why is that at the time I was still not 100% certain I wanted to medically transition but I was still extremely curious to try HRT. Most HRT-related changes are reversible but breast growth is the main exception since it is irreversible.
However, when I began on a very low dose (1 mg sublingual estradiol / day, no anti-androgen) I basically got the "worst case" scenario: breast growth began almost immediately with almost no other effects (which as I understand it is pretty unusual; breast growth usually begins after a delay of a few months on average). This put me in a position where I had to make up my mind on medically transitioning more quickly than I had hoped.
Buuuut, one thing I didn't appreciate until I began HRT is that all of the changes (including breast growth) happen so slowly that you don't have to make up your mind overnight and you have plenty of time to understand how you feel about them. And what I quickly realized was that after a tiny amount of breast growth they grew on me (pun intended). I quickly got emotionally attached to them and didn't want to give them up, and that was one of the early signs to me that medically transitioning was right for me.