take too much on
To accept or undertake too many tasks, burdens, or responsibilities. Between your job, the kids, and your volunteer work, I just think you're taking too much on! I've taken too much on at work lately, so I'm going to hire a new assistant.
take too much on
to undertake to do too much work or too many tasks at one time. Don't take too much on, or you won't be able to do any of it well. Ann tends to take on too much and get exhausted.