"The man who promises everything is sure to fulfill nothing, and everyone who promises too much is in danger of using evil means in order to carry out his promises and is already on the road to perdition."
Keep your promises always, never make a promise you are not 100% sure you can follow through on.
Actions speak far louder than words, we however live in the safest time in human history, proving you are a man of your word is ever more difficult as often we promise vague and meaningless things without a threat to defeat. It is also easy to make promises, unless you intent to do whatever it takes to keep them. Promise that which you can remember, follow through on and know you can do, everything else is a lie waiting to be discovered.