I recently had to stop working with someone who was unpredictable for me for a long time. It was simply not worth the pain.
I am not asking you to be punctual all the time. Neither I am not asking you to keep 100% of your promises. But I deserve enough predictability on your part so that I can go on with other things in my life without worrying about fall back plans with you.
If you are not organized enough to be reasonably predictable for your customers and friends, stop doing everything. Organize yourself before any new commitment.