There will be signs. You may sometimes feel that you just can't cope. You may have tense or sore muscles, stomach aches, headaches or problems sleeping. You may be much more tired or get more colds than usual. realize that you are smoking, eating or drinking more. You are less able to concentrate.
Simple tasks take longer to do.
It is important to realize that caring for someone takes time and energy. There will be limits to what you can do. You will have to decide which things are most important to you. Besides making choices, you will have to set limits on what you do in a day. It may be difficult to admit that you can't do everything.