Hardest Makeup Technique to Master?

The queen of winged liner herself! (source)

We all have one thing that we just can't seem to get the hang of when it comes to doing our makeup - and let's be honest, for 85% of us in this world, winged liner is our number one enemy. I don't know what it is but there is nothing I do that makes it easier! I'm not a fan of extremely exaggerated winged liner but I think a simple feline flick can look so pretty, especially when paired with a bold lip! 
Just last week I decided, "Hey, today is the day to give this whole winged liner thing a go!" A good 20 minutes later, I had two crooked patches of black eyeliner extending out of my eye that made me look like I'd been punched. So yeah, you could say it went well... I had to rush to bathroom and grab a q-tip and try to get rid of the mess I'd created before I left the house! Thank goodness for makeup remover! 
But seriously, is it just me or is this an issue for other people? There's all kinds of tricks, like following the line created by your lower lash line and using a soft, white pencil to draw the line before you go into liquid/gel liner so that you can fix mistakes. As good as that all sounds, I feel that the execution is what is challenging. You either get the line at an awkward angle or your line looks different when you close and open your eyes. There should really be a coming of age ceremony for girls and their makeup skills where someone could sit with us and just show us how to do it. Am I right ladies? 
Here's a video that could be helpful! (I'm almost sure that the problem here are my eyelids or something and that nothing technique wise that I do will ever allow me to get the perfect wing ha!)

So I'd like to know, what makeup techniques are the hardest to master, in your opinion? Are you with me on the deadly trap of the winged liner or is there something I'm missing? Makeup should always be fun and experimental. It's so fun to learn and try out new things and see how we can work with it ourselves! (Fun until you look like a bus hit you in the face, but that's besides the point, right?)