Get over being selfish- It's a basic truth that you have needs, and a simple way of defining needs is 'what you require in order to fulfill your purpose'. If you're a carpenter, you need your tools or else you can't do carpentry, and it's impossible for you to do the good things you do that make life better for other people. You have many purposes, and therefore many needs- you are someone's child, someone's friend, someone's parent perhaps- all of these roles confer responsibilities upon you, and fulfilling these responsibilities is arguably part of your purpose in life. If you fail to get your own needs met, you cannot effectively serve those purposes. Getting your needs met is an absolutely moral endeavor, because it establishes your own ability to contribute to the lives of others.
Being selfish doesn't mean taking more than your share- that's what the complainers would have you think- they want you to feel bad about not meeting their needs before yours. Being selfish is not the opposite of being generous, it is the pre-requisite of being generous. What being selfish does is allow you to fulfill your potential- it allows you to discover, and to express the values that define your purpose in life. It allows you to filter out demands of you that are unreasonable, it allows you to attract positivity and position yourself in a way that everything you do makes you happy, including giving.
If you're positioned in your life to get happiness out of everything you do (I get a lot of satisfaction out of giving gifts, it makes me happy, it's a selfish act) then you become motivated to do more- and in doing more, more people benefit from you, it's as simple as that. At the same time, you free yourself to reap the benefits of everything you do- and you realize your ability to fulfill your purpose in life.
"Our deepest fear is not that we are inadequate, our deepest fear is that we are powerful beyond measure. It is our light, not our darkness, that most frightens us. We ask ourselves, who am I to be brilliant, gorgeous, talented, fabulous? Actually, who are you not to be? You are a child of God. Your playing small doesn't serve the world. There's nothing enlightened about shrinking so that other people won't feel insecure around you. We are all meant to shine, as children do[...] it's in everyone. As we let our own light shine we give others permission to do the same; as we're liberated from our own fear, our presence automatically liberates others." -Marianne Williamson
Your first responsibility, before all others, is to meet your own needs. Until then, you're not only cheating yourself, you're cheating everyone around you of the benefits that you could have offered to the world, had you realized your potential. If your needs are not met, you cannot be happy, free, ethical, moral... because these are the values that express who you are after they are met. If you don't have what you need in order to be you, you can't do that. For this reason, it is profoundly immoral to neglect your potential, just as it is to ask another to do so.
If you are unprepared to serve yourself, you cannot serve others. Make yourself happy, and you will attract people who are, or want to be, happy. Accept that you cannot make anyone else truly happy- only they can do that, by following the same selfishness principle. Create within yourself what you want to attract from without- it works in no other way, and it starts with being selfish.
How to know you're getting better at being selfish:
* Your 'wants' are few.
* Your friends are happier
* You attract more people to you
* More and more of what you do makes you happy
Get over being right- Maybe another way of saying this is 'Quit serving your ego and train your ego to serve you.' Who is the boss here, after all? This one is fundamentally important, because mastering this concept is key to personal freedom, happiness, and being an effective person.
If it's your mission in life to validate all of your current beliefs, to prove yourself right at all costs, you are truly the servant of your own ego and you'll resist changing your mind, your beliefs, your opinions, your self, even in light of compelling new information. If you're unwilling to change your mind, you're unwilling to learn, grow, evolve, or adapt to your world, and this can become punishing, because your ego is a demanding thing- it needs a little stroking, and it'll take what it can get- even if it means putting the blinders further on and settling for feeling good about being 'right' when you don't get your way.
...but what is 'right', anyway? Being 'right', correct, proper, etc. is a subjective judgment you make when you process your observations of the world through the filter of your beliefs, habits, and values... but it is not an absolute, it's just what works for you.