Every lazy yes spends time your real yes needed.

Agreement is easier than refusal in the moment, so you commit to things you do not care about because saying no felt awkward for four seconds. The cost shows up later, when the thing you actually wanted arrives and finds your week already full. Nobody declines the important thing directly; they simply have no room left when it comes.

Before you agree to something, ask what it would displace. Give yourself a stock line that buys time, something about checking before committing. Then let the no be plain, because a vague maybe costs everyone more than a clear refusal.