Resources:

Randolph M. Nesse:

"scientists who study animal behavior recognize several different kinds of resources organisms seek. Personal resources such as health, attractiveness, and abilities are essential. Food shelter, and material resources such as money are essential. Modern humans get those resources by working at jobs or other social roles. Efforts to find, impress, and care for mates require substantial effort. So do efforts to help and protect offspring and other relatives. Finally, having allies and roles with recognized status in a group are keys to Darwinian fitness. Six kind of resources[.] 

Effort to get one resource take time and effort away from getting others. Foraging far from home will result in more food but will compromise safety. Time caring for children is not available for working or impressing potential mates. Brains generally make good decisions about how to allocate effort even without sophisticated conscious thinking. All animals make such decisions, from aphids to zebras."