To quote Nasser:

May 30, 1967: "With the closing of the Gulf of Aqaba, Israel is faced with two alternatives either of which will destroy it; it will either be strangled to death by the Arab military and economic boycott, or it will perish by the fire of the Arab forces encompassing it from the South from the North and from the East." 

May 30, 1967: "The world will know that the Arabs are girded for battle as the fateful hour approaches." 

The lesson here is don't threaten a country with extermination unless you are ready to back it up. Nasser did just that. Even if you attack first, wars have uncertain outcomes as the Arabs found out in 1948 and 1973. Jordan and Egypt realized this. Meanwhile in Syria, Saudi Arabia, Yemen, Iraq, Gaza...