The theme of this poem is that people are responsible for their own fate. The poet is saying that all people have the "equipment" to succeed. God has given them everything that they need, now it is up to them to determine whether they are going to use that equipment well or badly.
This sentiment reflects Guest's own background and his beliefs. Guest himself was forced to do all sorts of jobs as a young boy because his family had been hurt financially by various events. He then had to leave school before finishing high school because his father died. These experiences gave him the attitude that people can improve themselves if they will only work hard enough.
"Equipment" is typical of Guest's sentiments. It has a very self-reliant, democratic theme that is very much in line with what most Americans believe.
All are equal before the eyes of God. They are blessed with the same equipment. The difference is how we train ourselves to become great. Courage and determination are very much essential to become great in life. U urself are resposible for your own fate.