The character of Tin-Tin, that made Hergé famous, was originally some kind of an ideal depiction of himself.
However, during the second world war, he published comics in a newspaper 'stolen' by the German occupation. This brought him into trouble, although, finally, his case got closed. Yet the stress of the troubles, and the disillusions (he was temporaly banned from working, and some friends of him got condemned as collaborators), followed by marital problems, changed him completely. He had extramarital affairs, breaking up his marriage for a young employee but he deeply struggled with feelings of guilt towards his first wife he had abandoned.
So, he mentally 'separated' from the character of Tin-Tin, and identified himself more and more with the character of Captain Haddock, which he had put 'on retirement' in the castle of Moulinsart, spending his days doing nothing, and being no more bothered about anything. This setting made him create his masterpiece, one of the best comic stories ever made (to my opinion), 'The Castafiore Emerald' (1961). A story, wherein really 'nothing' happens, but which is so brilliantly told, no one notices.
At the end of his life, he stipulated that Tin-Tin would not be continued after his death. The last story, 'Tin-Tin and Alph-Art', was posthumously published in its unfinished state.
Hergé died today 37 years ago, on March 3rd 1983, aged 75.