我理解的是，成功指的是一个人在他的一生中能够实现他的主要目标的能力，这进而引出了成功和收入之间的关系，因为实现为你所爱的人提供一个美好的未来这样自然而然的目标，需要金钱。

另，part of 后面用复数名词似乎不合适。

I understand success to refer to one's ability to achieve the predominant part of his goals in his lifetime, which in turn leads to a correlation between success and income since the accomplishment of such a natural goal as to provide a good future for your loved ones demands the means

参考译文：我明白成功是实现一个人一生中主要目标的的能力，这种能力反过来有导致/产生收入和成功的之间关联，因为为了给你的爱人提供一个美好来的这样一个自然目标的实现/完成/履行需要这些物质收入/财富/金钱。

重点短语解析如下：

(1)refer to 指的是

(2)one's ability to achieve sth 某人实现某事的能力

(3)the predominant part of one's goal 某人的主要目标

(4)in one's lifetime 在某人一生中

(5)in turn 反过来，转而

Theory is based on practice and in turn serves practice.  

理论的基础是实践,反过来理论又为实践服务.

(6)lead to 导致，产生

(7)correlation between success and income 收入和成功关联

(8)since 因为；自从

(9)such a natural goal这样如此自然/必然的目标

(10)as to do sth 以致于做某事

(11)provide a good future for 为..提供美好未来

(12)your loved ones 你所爱的人

(13)demand the means 需要这些收入/财富/金钱

(14)the accomplishment of 对..的完成/实现