We should remember that industry is the key to success. (Passive) (Change the sentence)

A successful man is greater than any other asset to a country. (Positive)  =  No other asset to a country is as great as a successful man. 

However, being a successful man is a complicated task. (Negative)  = However, being a successful man is not an easy/effortless task. 

We have to be industrious to prosper in life. (Imperative) = Let us be industrious to prosper in life. 

The idle always lag behind. (Complex) = Those who are idle always lag behind. 

We must work hard so that we can earn money. (Simple) = We must work hard to earn money. 

By working hard, we can improve our lot. (Compound) = Let us work hard and/ and so we can improve our lot. / We work hard and/ and so we can improve our lot