STAND UP FOR YOURSELF!
DON'T GIVE ANYBODY THE POWER TO HOLD YOU BACK, DEAR.
Its time you redefine your boundaries. Decide how you are going to enforce them and why it is the right thing to do.Sit back & write this down on a piece of paper.
You have the right to say no to watching your neighbor's kids, if it would push you over the edge of sanity and make you grouchy toward your family. This is the loving thing for all concerned. You choose not to hold fear around how your neighbor will feel about this. You know it is the right thing, and that is enough. You go tell her with love that you can’t do it (without having to explain why). In the end, she will respect you for your honesty.
It is important that you stay true to yourself. That is what is going to matter in the end.If someone asks you to do something you're not comfortable doing, you say no kindly. They will have to respect you for you.
Taking the time to write out, on paper, exactly how you are going to choose to feel and behave really helps. You are basically creating an official policy for yourself. Then, read this policy often and practice enforcing it.
Remember, you can be strong and loving at the same time.
You must also ask how you can forgive yourself for being weak in the past. I say you look at these situations as perfect lessons, not mistakes. They have nothing to do with your value. They happened, so you could see what you are afraid of and learn to change it. Focus on the beautiful lesson this situation provided, and let the rest go. Remember, a man of principles is a man of honor.