While it’s true that not everything is about you, it’s also true that not everything is about others. If you have created a habit where you constantly operate out of balance, and feel that your time and needs are second to others, you mess up the “even exchange of energy” that must exist to feel good in any relationship.
If you tend to feel “bad” when you want to do something for yourself, I want to remind you to not confuse selfishness with making choices that are right for you. Why? Because the more you live your life according to what is best for you, the more joyful you become. Your happiness is the greatest possible gift to the Universe, and when your heart is at peace, it blesses everyone and everything it touches.