Others' reliability, not just a child's personality, affects their willpower.
Parenting is the ultimate long-term investment. Be prepared to put far more into it than you get out of it, at least for some time. Given the stresses of contemporary American culture, the happiness of couples plummets the minute they become parents.
Human beings are social animals, and the tenor of our social life is one of the most important influences on our mental health. Without positive, durable relationships, both our minds and our bodies fall apart.