To bite off more than you can chew means to take on a commitment one cannot fulfil.
An attempt to do more than you are capable of doing.
To try to do something that is too difficult.
1. We bit off more than we can chew for our school research project.
2. Are you sure you aren’t biting off more than you can chew for this new job?
3. You shouldn’t bite off more than you can chew and hire a planner for your wedding.
4. I have a tendency to bite off more than I can chew when it comes to family obligations.
exceed, go to extremes, go too far, overdo, overextend oneself, overreach, slave, spread oneself too thin, strain, stretch