Until we get older and then it starts to go away and it is LOVELY 
I feel so much more confident and happy going around the place now I haven't got the eyes on me all the time, and the other stuff. Not that I'm gorgeous or anything
but I think that all young women are watched and assessed and looked over in a not subtle way by so many men when they go about their business that even when you aren't actively aware of it your brain knows it's happening, we are all animals after all we know when we're being watched, when we are attracting the attention of others when we would rather not be noticed while we're just doing our stuff. I think it makes a lot of females feel self-conscious and uncomfortable even if we don't realise why we're feeling that way. You see a lot of women going around adjusting their clothes, adjusting their hair, often they aren't doing it consciously, and they often look uncomfortable. I know I used to do that and I think it is a consequence of not being able to relax properly when we're out and about.
I didn't even realise until 2 situations. The first was when I was very heavily pregnant and it stopped and it took me a while to work out what was so nice. And then on the tube a bloke looked at me and I turned and he stopped and I realised that was it, I didn't have all these eyes on me any more and it was lovely.
The second time was when I went to a feminism conference which happened to be pretty much all female there were only a couple of blokes there dotted around and again I wondered why I felt so comfortable and then I realised that was it.
Now I am in my early 40s and it's stopping, I feel so much more comfortable and confident walking around the place, it's lovely.
These are just my thoughts on how I've felt and what I've noticed, not saying these are definite "things" but for me, they feel right.