Just Say "No"
People will always try to place unrealistic expectations on us. They tried to do it in Jesus's day, and they will try to do it now.
For example, some of the people demanded that Jesus perform a miracle to prove who He was. Yet others followed Him not for Who He was but because they wanted Him to feed them.
We need to follow Jesus's lead. He never did anything simply becuse someone demanded that He do it, or to prove Himself. He did only what His Father told Him to do. Jesus explained this.
Then Jesus said, “When you lift up the Son of Man, then you will know that I am he, and I do nothing on my own initiative, but I speak just what the Father taught me. John 8:38 (New English Translation, NET)
If you can meet a need, and you believe it is the right thing to do, then fine- do it. But, don't allow people to pressure you into doing something when you know in your heart that you shouldn't. Yes, some things are right and need to be done, but you may not be the one God wants to do it. Or maybe doing it will stretch your time and energy too far. Or possibly now is not the best time for it to be done. At the end of the day, we all must do what God wants and not what people want. Of course, some people will not like this, and some may be downright angry at you. Regardless, we must please God and not people. And in every situation, God is looking out for your best interest, so you ultimately can't go wrong following Him.
Therefore, do not allow people to put more on you than you can handle. Establish boundaries by making it clear what you will and will not do. Learn to use that little two-letter word "no." You will end up with more peace, and those who care about you will respect your answer (and those who don't won't). Do what you can do based on God's direction and leave what you cannot do to Him. Be at peace and know that you can't do it all. As a result, you will not wear yourself out. Follow God, and don't be afraid to just say no. Then, go enjoy yourself and your life. You will be glad you did.