It seems rather simple to me. The more you give, the more likely you will be to receive. And even when I don’t receive, I just feel better when I give.
One of the things I try to do regularly is send out kudos e-mails here at work. I don’t know why people find it so hard to recognize and compliment the good works of others, but since I know I appreciate it when people do that for me, I try to do it for others as well. I’ll write the e-mail to their supervisor, my supervisor, the division head, and the person in question. I’ll simply state the good work that was done and how much it is appreciated. I’ll only do this if I sincerely feel it. (People can tell when you’re being fake.)
I also try to keep in mind what people find interesting, and then when I hear something new about that topic, I share it with them. People genuinely like being thought about. I know I do. When someone says, “This made me think of you,” it feels like a hug to me.
I’ve known plenty of selfish people in my lifetime. What I’ve observed is that when you turf guard or hoard the good things for yourself, or put your needs ahead those of everyone else, people stop trusting you. They don’t like you. They’ll hesitate to help you in your time of need. And you will therefore become even more bitter, selfish and angry. It’s a downward spiral.
The best way to stay off that spiral is to give, even if you’re fairly certain you’ll get nothing in return. Give, even when it doesn’t feel pleasant. Give, and let the universe take care of whether that giving was deserved. It’s not always easy. But in the end you, and everyone in your circle of influence, will be much better for it.