A teenager with a knife fixation stabbed his best friend with a dagger during a "childish argument".
Aaron McKie, 18, of Meadowbrook, Sandgate, was in custody awaiting sentence after being found guilty of wounding with intent.
Judge Adele Williams heard that while inside jail, he was seen drawing a hand holding a dagger - but claimed he was just designing a family coat of arms.
McKie was given an eight-year sentence including an immediate five-year jail term and a three-year extended licence.
The judge told him: "You have a fascination for knives. You completely lost your temper. You took a knife from your pocket and stabbed your friend twice in his leg and back."
The victim, William Otto, spent eight days in a London hospital after the April attack near the Tesco store in Cheriton, Canterbury Crown Court heard.
One of the wounds had damaged a kidney, but Mr Otta has since made a "good recovery" physically - although he still suffers psychologically, the court was told.
Paul Hogben, defending, said "events had spiralled out of control" after McKie had downed "at least 20 beers" while taking medication.
"Then he was in a public place with a knife that he shouldn't have had and he got into a childish argument with the victim.
"If he hadn't had the knife then it would have been nothing more than an argument, but because he did it ended up with him injuring his best friend."
McKie already had a previous conviction for an attack with a potato knife and had a bust-up with his sister.
Mr Hogben said: "He got into an argument with his sister and they both ran to the kitchen and they both picked up knives. That incident didn't lead to any criminal proceedings."
"You have a fascination for knives. You completely lost your temper..." - Judge Adele Williams
He said McKie got in with a group of people who had encouraged him to drink, adding: "And that lit the blue touch paper which led to this event."
After the stabbing, he ran away and hid the weapon although he later led officers so it could be recovered.
Judge Williams told McKie: "I have concluded you do pose an ongoing risk to the public because of the previous conviction and because I have seen and heard you give evidence."