You leave out the rest of the part of the passage that provides context because after I reading it seems he is more frustrated on his ability to govern than anything else.  The president became angry and lambasted the Attorny General for his decision to revuse from the investigation stating "How could you let this happen, Jeff?" The president said hte position of Attorney General was his most important appointment and that Sessions had let [him]down," contrasting him to Eric Holder and Robert Kennedy. Session recalled that hte president said to him "you were supposed to protect me" or words to that effect. The president returned to the consequences of the appoint and said Everyone tells me if you get one of these independent counsels it ruins your presidency. It takes years and years and I wont be able to do anything. This is the worst thing that ever happened to me