It’s not always possible to put right what you’ve got wrong. That’s not to say you can’t do anything – a sincere apology demonstrating genuine empathy, understanding and remorse will likely help. Actions speak louder than words though, as always.
This doesn’t mean spending money to make it better. It doesn’t mean bake a cake and expect things are patched up.
Giving your time and energy to make amends might mean helping the injured party on something unrelated. It could mean working with them on the substitute for what you’d said you would do. When the opportunity to deliver on the promise you made has gone, can you make a better promise – and keep it?