It's a well known fact that the statement “What goes around, comes around” [reference] is widely used by many people in the world. However, the phrase was first used by Eddie stone in 1974 For me its more like a cycle and it implies that whatever you do in life to anyone in any way will sure come back to you. In that same regards what ever effort you put in any aspect of life will surely yield results relatively to the amount of effort you put in. If you put in more pressure you will get more results, if you put in less pressure you will get little or no result.
Further, when relating the saying to Karma, we can consider the golden rule which actually cuts across many religion, like the Buddhism, Islam, Christianity, Judaism, etc, the rule actually entails we treat others as we’ll like to be treated. [ref]. In other words, If we treat people wrongly, we get same treatment from others, just like karma you get what you deserve more reason why I like this quote so much. It actually guides ones way of living.
In addition to this quote, there are other similar references but I will be considering the one from the bible “Be not deceived; God is not mocked: for whatsoever a man soweth, that shall he also reap” [reference]. This is just a more simplified way to explain the quote with reference to the bible. Its more like an overview, that whatever you do in life, whether in the dark or beneath the sun you will surely reap it. It becomes imperative to try as much as possible to be positive in our ways, and extend that positivity even unto others.