How we think about and treat others will affect us.
Check this out:
"Do not judge and you will not be judged. Do not condemn and you will not be condemned. Forgive and you will be forgiven. Give and it will be given to you. A good measure, pressed down, shaken together and running, over will be poured into your lap. For with the measure you use it will be measured to you." - Luke 6:37-38
Have you ever noticed how stingy people never have enough money. On the other hand, some people who are generous still seem to have an excess after all they give away. Now some may say, it is easy for those with a lot to give something away - of course they still have plenty left - but me, I haven't got much.
Someone once said, you cannot receive unless you have open your hands and this is one way I think of this verse. If you are in the habit of giving, money and resources have a way of finding their way to you. You will no doubt know people who exemplify this reality in their life.
This is not all about money though, don't judge or condemn and you won't be either, forgive and you will be forgiven. These ones are potentially harder to quantify in a way that can be compared from life to life however the presence of judgementalism, grudgeholding and condemning people can certainly be detected as can those who are freeing, encouraging and generous spirits.
The big key about this passage though is that this isn't simply Karma ie. you do something good and the universe does something good for you, this is God. When it comes down to it, whatever we do will be seen by God and it is him who ultimately oversees what we receive. As the last half of the passage illustrates, what God gives to us always exceeds what we give.
If I was going to sum this passage up in just two words I would say - Be Generous - be generous in allowing people the benefit of the doubt, be generous in building people up, be generous in giving to people what you have... be generous!