Why do my abilities activate so slowly?

The title may seem a bit misleading of what I'm talking about, but here it is. I really need to be a better Riven, as she is my favorite champion, so I started watching higher tier players when I have the chance. I noticed this when I saw other people play Riven, not just the higher ups, but everyone seems to be able to activate Broken Wings in a much quicker succession than I can. Now it might sound like I'm talking about the combos, but I'm not, I'm talking about just using Broken Wings 3 times in a row, very quickly. I can't tell what I'm doing wrong, they can just start and finish all three strikes in roughly 1-1.5 seconds, while I take a decently longer time to get them off. I would very much appreciate any non-sarcastic help with this, so please, well, help.