Several years ago a woman wrote to Ann Landers asking for advice on how to respond to her mother-in-law, who continually borrowed things and didn't return them. The concerned woman was afraid to say anything because she wanted to stay on good terms with her mother-in-law - who was otherwise in her words "a wonderful person." Ann Landers appropriately gave this advice: "This is going to be a lifelong problem unless you replace the spaghetti in your spine with a backbone."
The moral here is that it doesn't cost much to be kind - but it can be very costly being too kind. Much like the woman who wrote to Ann Landers, many people are so obsessed with being accepted by everyone that they put themselves through emotional turmoil by being too kind. They fear they will hurt the other person's feelings and be rejected by the other person. Sometimes it would be far better, however, if they weren't all that kind and instead gave other people a good tongue-lashing for expecting too much.
As a matter of course we all fall into the trap of being too kind to others at some time or another. Clearly, we must not let the urge to be kind or nice to everyone interfere with our being successful and happy in life. "The disease of niceness cripples more lives than alcoholism," British actor Robin Chandler once remarked. "Nice people are simply afraid to say no, are constantly worrying about what others think of them, constantly adapting their behavior to please - never getting to do what they want to do."
Granted, being flexible and adaptive and accommodating are valuable character traits. Nonetheless, you don't have to listen when a friend or acquaintance runs on for hours about work, family, girlfriends, or rude checkout people. If you are uninterested in hearing more, say so immediately. Otherwise this person will cost you a lot of time and energy that you can utilize elsewhere.
There is nothing wrong with being generous with your time now and then, but constant acts of generosity will lead to certain people expecting this from us forever. As author Harvey Mackay wisely pointed out, "If you want to be a Santa Clause, your sled better be able to pull a trailer." The more you give to certain people, the more they will push their luck.
Being kind to someone by saying yes when you really wanted to say no will cause pain in the long term. If you are too easy going, someone will try to take advantage of you by seeing how much work or how many favors they can extract from you. You don't have to feel obligated to say yes just because the person is your friend. If people are trying to take advantage of your kindness, you have to let them know in no uncertain terms that you don't exist for their convenience.
The ability to say yes or no when you mean it defines your personality and what you stand for. Don't feign agreement with someone in the hope of being in higher standing with that person. You will have wasted time, energy, and money satisfying someone else's desires at the expense of your own happiness and sanity. As a result, you will end up resenting yourself and the other person for having said yes.
In short, discard the notion - forever - that you have to be kind to all people. Being kind to all people can leave you giving so much of yourself to everyone else that you have become nothing yourself. Your willingness to take risks and experience life to the fullest will be severely compromised.
Luckily, there's no obligation - moral, legal, or otherwise - to be kind or generous to everyone. It follows that you should be kind and nice only to individuals who deserve it and when they deserve it. Keep in mind that not everyone has earned the right to receive you in a nice mood all the time. Be as flexible as your mood allows, but don't bend over backwards to accommodate someone just because that someone is a colleague, friend, or relative. Ultimately, it comes down to this: Do you want to please everyone or do you want to please yourself by experiencing satisfaction and happiness in your life?