Discuss things that are age-appropriate with them, and don’t expect them to help you carry your adult load, whether it’s emotional baggage or physical responsibilities. (I don’t mean age-appropriate chores, which are good for a child’s develpment.)
Your children didn’t ask to be born, and they certainly didn’t ask to be a go-to choice for a sounding board when you’re struggling in life.
Children are not equipped to be your “person” in that sense.
Choose a safe adult. Let that adult be the recipient of your venting. Let them listen to you rant. They are more capable of dealing with adult stresses and adult emotions.
Better yet, work with a professional therapist who can help you handle your difficulties in the healthiest possible way.