-A person has the ability to cause many things through his speech.
-There are many varying levels of speech. A person must be able to channel energy through his words if he wishes them to be effective. This can only be done if a person experiences the words as he says them.
-When one has gone through an experience in the physical world he is then able to meditate on it and place that energy in his words.
-A poor person that has experienced bitterness, places this in his words as he curses. He might not even be doing this consciously but as he speaks he feels the words since he has passed through them himself. His curse is therefore very powerful. His blessings on the other hand are very weak.
-The opposite is goes for a wealthy person who is used to being subject to blessings and occurrences working out. When he blesses the words stem from these experiences and draw from them.
-Both the curse of a wealthy person and the blessings of a poor man will work to some degree, since everyone experiences all situations to some degree.
-Meaning, a person can only meditate on something he has experienced to some degree. Energy can only be transmitted through words if they are bound to the mind.
-This is the meaning of what G-D told Avrahom “I will bless those that bless you and those that curse you I shall curse” switching the order.
-The people who liked Avrahom and were likely to bless him, G-D blessed them first so that more energy shall flow upon Avrahom.
-Those that disliked Avraham were not cursed until afterwards, so at the time they would try to curse Avrahom it would be weak and relatively in effective.

(Sayings of GRA at end of Migilat Rus)