of all great relationships
The best context for the best relationships
When we can find a way for my selfishness (both long-term and short-term) and your selfishness (both long-term and short-term) are mutually supportive (synergistic), then we have a great win-win relationship. If we can't find a way, then the best relationship is either no relationship (or no particular transaction) or a relationship with more boundaries (where it works for both of our selfishnesses). Any other type of relationship is a win-lose, lose-win, or lose-lose relationship.
Why did God put you in your body and mind?
Because God/nature put you in your body and mind, your #1 job is to take care of yourself. Because God/nature put me in my body and mind, my #1 job is to take care of myself.
And who is the judge?
And, even though you may listen to others, ultimately, you are the best judge of what is in your interest. And, the same is true for me: I am ultimately the best judge of what's in my interest.
Sometimes choosing courage is required to ensure you are taking care of yourself in any particular relationship or transaction, especially since it may not "look good" to be selfish. In addition to choosing courage, the way you take care of yourself (in order to maintain the best possible relationship) can be quite important.
For example, here in China some friend will often ask me to help them to improve an English paper that they have written. I really don't enjoy spending my time doing this, especially in comparison with all the other options I can choose from. I will reply to my friend, "A part of me would like to say 'yes' and help you out. But, I don't enjoy doing this type of thing and I don't know how I could still be taking care of myself if I did. I hope you can understand and find another way to get what you need." My friends seem to understand and accept the fundamental principle of "win-win."
If they could not accept this principle, then I would choose not to have such a friend.