When you are practicing a technique or combination you need to learn to execute the technique correctly, that’s pretty obvious isn’t it?
So in order to do that you need… a strong balanced stance, use the appropriate blocking or attacking tool, correct starting and finish point of the technique, know how to use the body’s hip rotation to increase power, control your breathing, focus on the target, relax the muscles as you move etc.

That’s a lot to think about, but it has to be done, and, repeated often in order for you to be able to do that technique correctly.
You know that, so you practice diligently in order to be able to do it well.

Then you begin putting in more power and performing it in a flowing movement that starts to make it all come together. Next you ramp it up and really deliver a fast balanced coordinated powerful technique. Congratulations you are half way there!

Now comes the hard part. You have to learn to use it.
Doing and using are two related but completely different aspects of performing that technique.
You need to visualise its use in an attacking or defensive environment depending on the techniques use.
When you practice now, you need to visual the technique being used on and against an opponent.
In your mind’s eye see the result of your action, do it again and again against the opponent you can ‘see’. Look at angles, distances and speed. Look at the openings that are available after your attack or defence movement and what could you follow-up with. Now practice with a partner in as real a way as possible, this will give you the correct ‘feel’.
In future, when you are practicing alone without a partner you will be able to truly use the technique against your imaginary partner, and be able to practise using it over and over.

So now you know the difference, when practicing alone, of doing and using.