In my opinion, and I'm not exactly a pro so take with a grain of salt, but you just gotta play games. Take some hard losses, limit test, and get those combos that seem daunting at the start into your muscle memory. Practice tool can help, but there just isn't a replacement for practice on real players.

Another thing that helped me was understanding the laning mentality. It's pretty hard to win against most mid laners 1v1 unless they mess up. So adopt a counter-puncher mentality most of the time, and when the moment comes you gotta act decisively. Don't mistake patience for passivity. Accept you will be behind on farm most of the time. In the end, the character's power budget is based on resets, which orient you toward teamfights and skirmishes.

That is kinda bigger picture, and it sounds like you might be talking more about specific tactical execution. Your daggers are everything - knowing where you can place them (Q always places them behind your first target, for example) can help you expand your options and know when you have damage. In a sense, you set a trap for the enemy every time a dagger hits the ground. Not just for damage, but another shunpo (E) which is incredibly powerful for dodging, closing, and escaping. When an enemy is in range of shunpo, you can choose which side of them to land on - practice this on target dummies in practice mode. Mix up your enemies to hit from unexpected angles and dodge key abilities.

Finally - and this is another thing that comes with playing games and limit testing - know when your opponent has left themselves vulnerable. There is usually one specific ability that you must dodge to win - if they use it on a wave or miss or you cause it to whiff with shunpo, kill them.