Confused about the 1-2-3 combination

I have a question. When you throw the 1-2-3 combination (the Jab-Cross-Left Head Hook), you move inside with a quick 1-2 that isn't really hard, but is fast and blinds your opponent's vision (meaning the 1-2 is a distraction, as opposed to power shots). Then you follow it up with the Left Hook, and whatever else right?

The way I've been throwing the 1-2-3 when shadowboxing and hitting the heavy bag was throwing the 1-2 at full power while moving in, and then throwing the Left Head Hook. When I threw it like this, is was extremely slow and lacked flow to it.

Any advice is greatly appreciated, thanks.

Well first off you want the combination to flow with some speed. I suggest not putting much power on your punches when you practice and just let your hands go. Next, you need to realize that the importance of the 3 is not only that it's a solid power punch that works when your opponent's guard is concentrated to infront of their face, but ending the combination with the punch puts you in a better defensive position than ending with the 2 which leaves you wide open for a counter. Lastly, to help landing this combo I suggest that you switch up your rhythm, instead of firing off a 1,2,3 one punch right after the other every single time you can throw a 1,2(pause)3 and catch your opponent before a counter or you can throw a 1 (pause) 2,3 and do the same. Changing rhythm makes you less predictable and it could lead to your opponent guessing what you will do and moving into a power punch.

I hope that helps