Generally, when you say that 'something is somebody's own doing,' you are saying that it is their fault; that their mistakes or poor decisions have led to that outcome. For that reason, it is often utilized as an accusation or as an admission of blame, and is similar to the phrase 'you have no one to blame but yourself.' However, this expression can also be a means of crediting yourself or somebody else with something, sharing a similarity with 'thanks to me.'

1. The company's financial difficulties are all my own doing. I have made some terrible decisions over the years.
2. Person A: "Well done, I hear your student got an A in her exam." Person B: "That was her own doing. My input in it was minimal."

1. This mess is entirely your own doing, so stop blaming others and get it sorted!
2. Person A: "Well done! I hear your student got an A in her exam." Person B: "That was entirely her own doing. My input was minimal."