I'm hard pressed to understand why you don't have an identity, boundaries and a life of your own. Now if you're under the age of 18 I would understand that you don't know any better but if you're older then why is your life so tied to hers and why is your focus on your sister? If she's toxic then why haven't you found some distance? Weird that you want to do stuff for her.

Remember, this person can only affect you how you let it. I have a beautiful friendship with a lovely gal but she can be toxic so at times i sort of listen on auto pilot, i dont get involved directly with whats going on but do offer suuggestions (usually shot down), and when I have to spend time with her again not let her digs go very deep

It helps to start doing stuff for others who either deserve it more (true friends) or need it more (charity). That may help distract you from unnecessarily helping someone who doesn’t want or appreciate your help.

I agree, setting boundaries are important. We don’t have much to go on with the statement “I can’t stop doing stuff for her.” Not sure how to address the dynamics of your situation with what’s been shared and there’s a lot that I know is unsaid. On the surface, I would say that we have a choice “to do or not” and with sibling dynamics, I’m not sure how you are being manipulated (over the course of a lifetime) and making a shift now to break the cycle will require a lot of courage; it is possible, and you can do it. I recommend seeking out a great Employee Assistance Provider (EAP on your job which may be covered in your Company benefits) Counselor/Family Therapist that you can work with confidentially to provide tools, help to unpack, and build you up with a supportive construct to make the changes that you are seeking. The long game would be to emerge with a healthy relationship with your Sister as adults that you can carry forward for the rest of your lives. Sending heartfelt blessings to you to achieve the goal that you are seeking with your relationship with her.

I'm sorry to hear you are going through this! It is rough when you think you cannot say no but you most certainly can! People will take advantage of you so long as you let them, set boundaries, let them know where you stand and come to an understanding. I know this is easier said than done, but you got this!

My suggestion would be to set a limit on what you are willing to do for her. You decide what the boundaries are that work for you with your sibling, what you are willing to do and what you are not. Then you have to be consistent with holding to the boundaries of what you are really not wanting to do despite some likely awkward discord and tension in the home. Set boundaries that you feel you can uphold and be consistent. Its not easy but consistency is key.