I honor my feelings and energy levels by setting boundaries. I am safe to say no whenever God has guided me to do so.
There are other ways to help, even through prayer.
We try so hard to not cause confrontation with others. We go out of our way to help others, even at the cost of depleting ourselves. Then when we become depleted, we sometimes become resentful.
Resentment surfaces when you are too exhausted to lend that helping hand, but you do it anyways. This may also occur in relationships where you feel you are giving way more than you are receiving (including satisfaction and even joy).
These experiences are examples of signs that you need to set boundaries in your life. This is beneficial towards your health and also your happiness.
When it comes to someone asking for help, seek God for guidance. He will notify you with the best response that's for your benefit. If you sense any negative feeling, this is a sign to hesitate before answering yes. And this is the time to seek God. Tell Him your honest thoughts and emotions towards this situation. He will guide you with the clarity you need. You just need to be open to receiving it.
Being true to yourself and setting boundaries will help you stay at a high, loving energy. This is what will benefit you and others around you.