“Soon” is a feeling. “By Thursday at noon” is a promise someone can plan around.

Vague timing moves the work onto the other person. Soon means whatever it means to you, so they have to guess, chase, or plan around a gap, and each of those costs them something. A date and an hour can be relied on, and just as importantly it can be missed honestly. Specificity is what makes a commitment real.

Replace the next soon you are about to say with an actual day and time, even if that time is later than they hoped. People accept later far better than they accept unknown. If the date slips, say so before it arrives.