Seeking Guidance on How to Explain My Departure

Hello, I hope this question fits here. I recently resigned from my dream job after six months due to an overwhelming workload, often putting in 10-11 hours a day and sometimes working weekends. The company was contracted for a project that wraps up in December, and I decided to leave before its completion. Now I’m applying for similar positions with permanent contracts and I’m unsure how to explain my departure when asked about leaving the project early. Any advice on how to navigate this conversation would be greatly appreciated!