Sentence:  If you are a good way ahead, and particularly in the last hand but one, if you have a chance of winning a <WSD>Rubicon</WSD>, you should make a safe discard, with the view of dividing or winning the cards, in order to keep your adversary back. On the other hand, if the score is much against you, and you are under a <WSD>Rubicon</WSD>, you are justified in making a bold discard. 
Meaning of the word marked with <WSD> tags:  Especially in bezique and piquet: a score which, if not achieved by a losing player, increases the player's penalty.