In a nutshell

[ladyramkin2000]

No: HPFGUIDX 105765

I was really impressed by a passage in Charme's recent post:

"He (Snape) knows from experience just the kind of weaknesses 
Voldemort exploited in him, and needs to impress the urgency on Harry 
his suspicions of the results if Harry doesn't succeed "(in 
occlumency, that is).
Doesn't that just hit the nail in the head! Snape is working from 
personal experience. Voldemort had sensed the weakness in him and 
used it to recruit him to his own side.  Snape is probably the only 
person who has had this experience and is in a position to use it to 
stop Harry going along the same path.  That must be the reason why DD 
chose him to instruct Harry, together with the fact that Snape is an 
acknowledged superb occlumens, both these reasons outweighing the 
fact that neither Snape nor Harry are going to be happy with the 
lessons.  I think this makes a lot of sense

Sylvia