Some psychologists argue that there is no pure altruism, that we help strangers (or animals), there must always be some benefit to us, even if we’re not aware of it.
Maybe helping others makes us feel good about ourselves, we gain the respect of others, we may look more attractive to other...

The task will seem less daunting if we tell ourselves that we are going to only spend five minutes working on it. 

We’ll find ourselves continuing to work past the committed time that we told ourselves.

We fear that others will not respect our boundaries. We focus on others and lose clarity about ourselves.

If we love and respect people who tell us no, they will love and respect our no. Freedom begets freedom.