Brevity is the child of silence, and is a credit to its parentage.

Short speech comes from being at ease with saying nothing. People who fear a pause fill it, and the filling is where most excess words come from: the restatement, the qualification, the joke to cover the gap. Once silence stops being uncomfortable, you say the thing and then stop, which reads as confidence though it is really just tolerance.

Practise leaving pauses where you would normally fill them. After you answer a question, do not add the extra sentence. Let a conversation sit for three seconds and watch what the other person does with the space.