Does anyone have any pointers as to how I can train ChatGPT on my personal corpus and create my own personal assistant?

Check OpeanAI's tutorials [1] and cookbook [2]. Or try LangChain [3], which abstracts a lot of the work.

[1] - https://platform.openai.com/docs/tutorials [2] - https://github.com/openai/openai-cookbook [3] - https://github.com/hwchase17/langchain