You don’t have to answer the second a message lands. Thinking time is allowed.

Fast replies have become the assumed default, so a gap now reads as a statement when it used to read as normal. Nothing about a message arriving obliges you to answer in the next minute, and the answers given within that minute are usually the worst ones you will produce all day. Thinking time is allowed and nobody actually minds.

When something needs a real answer, send a line saying you will reply properly later, then do. For anything heated, give it an hour. The reply you write after dinner is almost always the better one.