No act is 100% selfless.
There is always something that you gain in anything that you do.
Even in the case where you make the ultimate sacrifice, your life, you gain a bigger legacy.
Don’t back down from an action where you benefit because you don’t want to be selfish. Focus on acts where you gain and the other person gains.
On the flip side, there are selfish acts. A selfish act is where you benefit at the expense of another person. THese are the acts to be avoided.