Let people finish their sentence. Interrupting tells them you only heard the half you wanted.

Cutting in proves you stopped listening somewhere in the middle and started composing instead. Even when your point is right, the interruption becomes the thing the other person remembers, so they repeat themselves rather than consider you. The end of a sentence is often where the real point was hiding. Waiting three seconds is cheap and changes the whole exchange.

Pick one conversation this week and let every sentence land. If you lose your reply while waiting, it probably was not important. Notice how much more people tell you once they know you will not take the floor off them.