Keeping a promise when it got inconvenient is where your word actually gets its value.

Promises get their value from the ones kept after they turned inconvenient. Anyone can follow through when the day stays clear, so the weight comes from the times the weather changed, something better came along, and you went anyway. That is the point where your word starts meaning something to other people.

Be slower about agreeing and firmer once you have agreed. Before saying yes, picture the actual Saturday it will cost you. If you already said yes and now regret it, go this once, and be more careful at the promising stage next time.