You might have heard that story abt how God created a donkey,dog, monkey and man with 50,30,20 and 20 years respectively. The donkey refused 30 years of his life, dog 15 and monkey 10 years each.
But man being man, asked for the 30,15 and 10 years of the animals life, as he found 20 to be too short. God granted his wish!! from then on, Man lives 20 years as a man; then for 30 years as a donkey, toiling and sweating ; the next 15 years guarding his kids house while they go out to work, and the last 10 years like a monkey playing tricks to amuse his grandchildren.

Jokes apart, according to the Vedas, a mans life is divided into four ashramas:
1. Brahmacharya : the student life
2. Grihasthasrama : the family life
3. Vanaprastha : a life detached from material possessions
4. Sanyasa : renunciation of material possessions and emotional ties and meditation in solitude.

Stages of life I think childhood, teenage and oldage, this are the three main stages

Childhood,is one stage where child grows in the shade of his parents. Teenage,is the age where child become student,tutor and even expert in various field. In middle age,his study and experience give him/her good job and so he/she can take responsibility of his/her parents and family. In old age, is such an age where one should enjoy till his/her last breath.

1. Childhood
2. Youth
3. Middle age
4. Old.