So the key is not to try to try and jump straight from the beginning to the single carry on bag. Instead of focusing on paring back to the perfect capsule take a few months to get to know your clothes.
Give yourself a shopping ban. Set aside an amount of time where you don't allow yourself to shop for anything, not even second hand (plenty time for that later), when the prospect of getting more is removed you will see that you have enough (not the perfect wardrobe and you will improve on it later) but plenty, in fact even more than enough (but more about that in another post).
When I started out I didn't have a capsule wardrobe or a sustainable wardrobe even in mind, I had decided to do a buy nothing new year (because I knew I would be moving country late in the year and every time I move country I throw out (donate) a load of clothes), and because I was living in Colombia at the time there wasn't the same selection of charity shops we have here, so for the 1st 6 months I didn't add to my wardrobe at all (except for no less than 2 sets of ankle socks gifted to me...some of which are still unworn waiting for my supply to wear out).
During the 6th months I went through several phases and pit falls (others armed with more knowledge and a clearer goal may get through this whole process quicker).
The month before (I knew the ban was coming) despite my best intentions I stockpiled! Only things I considered essential like knickers (6 pairs) and a cardigan (I had a least 7 at the time) and I feel like I probably bought a t-shirt or 2 but they meant so little to me I have forgotten about them now. My advice to you would be to skip this stage...instead of planning to stop shopping at some future date, stop now. you may think there is stuff you need...but you survived yesterday and today without it, so you won't need it tomorrow.
In phase 2...when I started out with my ban, I kept seeing things that I "needed" for my wardrobe, that I hadn't been able to find before, at the time I didn't know that I was going to make a permanent change so I had started a mental (and possibly written) list of stuff I was going to buy once the ban was lifted. I am ashamed to say this phase went on for 3 months.
This phase also involved hoarding, I kept stuff that I knew was at the end of it's life, or didn't suit me or my lifestyle, just because I wasn't going to be able to go out and buy new stuff, now I needed it. (Suffice to say all that stuff as well as the panic buy cardigan etc has all been cleared away)
I don't think this phase is too damaging, assuming you don't actually go out and buy the things on your list, hoarding for a month or 2 isn't going to make a huge difference (but if you can take my word for it that you don't need this stuff all the better).
Eventually I came around to the idea that I had too much, I started to be able to clear out and donate some things, I was getting a clearer picture of the kind of clothes I wore, and that even after months of not buying any I still had far more than I needed and was never caught out.
So basically what I am saying is that you have more clothes than you need, and you can prove this to yourself by imposing a shopping ban...and then you will be able to move on from there!