As an adult looking after a child much of the day can feel like you reprimanding or disciplining the child when they do something inappropriate. But if you replace the idea of discipline with guidance, you’ll create a calm atmosphere. Discipline has its place, but often is not needed for day to day situations.
Much of raising a child is about educating them on appropriate behavior, so keep the guidance short and clear. “Blocks do not go in the mouth, blocks are played with using our hands”. I use a sentence composed of two parts: stopping the undesired behavior and stating the expected behavior. Drawn out explanations tend to be more confusing than helpful, so I only say what is necessary.
And remember to smile, be calm and polite. Being respectful will get you farther than any reprimand. Even infants who may not cognitively understand the words will often understand the intent. The earlier you start calm communication, the earlier they will follow your lead and the more peaceful your home will be.