There's a lot of advice here about using technical means to block youtube. If that works for you and solves your problem then fantastic. I am genuinely happy for you.

However, I suspect it won't. It never worked for me.

Firstly, any blocker you setup yourself you can take down yourself. You might find that it works for a day or two but then you feel really awful and binge youtube even more than normal.

Secondly, blocking tools are a tacit acknowledgment that you have given up and can't control yourself. "My willpower is just too bad. There's no way I can control myself. I need a tool to do it for me." This is the opposite of the feeling your want to cultivate. You want to feel more in control of yourself and your actions and be able to direct your attention accordingly.

Unfortunately, there are no silver bullets. There is no one little trick that will solve everything for you. That said, there are things you can do that will help a lot.

Get in touch with your emotions. Find out what triggers send you to youtube. Here's an example for me:

Think about important essay that is due soon --> worry and dread about academic performance --> watch youtube to forget about it.

This is probably happening in a blink of an eye. Probably so quickly that you don't even notice. If you can start noticing and naming your emotions you can deal with them more constructively.

Positive emotions can be triggers too.

I'm so excited about this new hobby I'm into --> I'm going to research it on youtube --> 3 hours watching videos about painting but not doing any painting.

Now, there's nothing inherently wrong with this. But if you can notice the emotions you can start to redirect them and work with them.