Dial it back

To dial it/something back is to reduce the amount of it.

You might see this expression in a recipe, for example: "If you don't like it too spicy, just dial back the amount of chill pepper."

Or I might write in an email, "I'm dialling back my business travel for the next few months."

This expression is easy to visualise: you can think of turning a dial to reduce the volume of music. I realize that this pretty analog for today, when you will usually see a slide bar for volume on your iPhone, etc. But back in the day, radios and stereos had a round knob for the volume. You would turn it to the right to make it louder, and to the left to "turn it down."