Yes sometimes others will take advantage of your kindness...funny thing is family has been the most likely to do this in my experience. Distant family, but still family. This tends to cause me to close off for a short period and then something simple like running ahead and opening a door for someone pushing a stroller and the thank you given reminds me that just because some people are jerks doesn't mean we need to start being one ourselves.
Nothing is on auto pilot, everything is created by our actions.
This right here is a fact of life people need to understand. Nothing good in life happens with first taking action.