Tips on keeping patient and calm

Hello My 14 year old daughter has autism, recently diagnosed although we have known for a long time. Even with this information, I can find it difficult to keep calm and patient with her. She is running out of time to complete her half term home work for school but just won't make a start. Transitions are difficult. Any tips on how to motivate her to do stuff she needs to do? If it is something that interests her, she does it no problem, but we all have to do some stuff we don't want to do, right? Appreciate any advice!