Every time you say yes to the wrong thing, you run out of hands for the right one.

Yes feels generous and free, which is why it is easy to hand out to whatever asks first. The cost shows up later, when the thing you actually wanted needs a Saturday you already gave away. You are not short on motivation at that point. You are short on room. Most crowded weeks are not built from bad choices, just from early ones.

Before agreeing to something, check what it is spending. If the honest answer is the exact hours you were saving for the thing that matters, say you will get back to them and mean it.