How and when does one not invest in others in Buddhism?

It is my understanding that there were instances that the Buddha discontinued the teachings to a number of people. Putting aside the concept of me and others, i am often in the situation whereby i have continued to demonstrate that there are better ways to a given situation e.g. conflict, methodology, etc. People often continue down this path where it often leads to the very situation that could be avoided. This in turn results in more conflict, distrust, etc. This often leads to a moment of befuddlement since i am unable to comprehend the nature of people. Although we appear to have evolved and consider ourselves civilized, rather than direct conflict, these often result in passive aggressiveness which further erodes relationships and growth since now people harbor negative or non-conducive emotions. It also requires substantial emotional, mental and physical investment to help others. How does one step away from 'teaching' or 'imparting' to others especially if one is in regular contact with them and depend on them to complete their responsibilities?