Liam Hanley, 32, was cleared of the attempted murder of Sarah Harries after a trial in March but convicted of causing grievous bodily harm with intent.
Sarah Harries suffered 39 stab wounds including having her throat slit when she was having a bath at her flat in Sussex Wharf on September 4.
She received life-threatening injuries and was only saved by paramedics because she was able to dial 999.
Hanley - who has been held in custody since his trial - appeared at Hove Crown Court for sentencing this afternoon.
'I will always have trust issues now'
In an emotional statement in court, Miss Harries said she still feels afraid in her own home.
"I will always have trust issues now, especially with a future partner.
"A few times I have had a bath and suddenly panicked and had to get out quickly.
"People ask whether I should move but this is my home. It isn't about where this happened because if someone wants to find you they will find you."
She told the court how she can feel people in the community staring at the long scar across her neck, a reminder of what Hanley did to her.
Defence barrister: Hanley did not start the attack
Defence barrister Rebecca Upton described how there had been no previous incidents between Hanley and Miss Harries.
She said: "It is an undisputed fact that Miss Harries had taken drugs that day despite the fact that she denied it.
"The evidence as to who took the knife into the bathroom was that it was not Mr Hanley.
"If that is right then it must also follow that it is Miss Harries that initiated the attack."
Miss Upton described how Hanley has a long history of drug use and had been homeless for several months in his early years.
"He hopes he can used the facilities within the prison establishment in order to better himself."
Judge: You entered the bathroom with a kitchen knife
Sentencing Hanley, Judge Christine Henson QC told him: "Your offending on September 4, 2018 remains an unexplained, vicious assault on your then partner who at the time was in the bath in her flat.
"For reasons that remain unclear you entered the bathroom with a kitchen knife. Your first action was to slice across the neck of your victim in the bath."
Judge Henson rejected the idea that the knife had been in the bathroom before Hanley entered.
"There were 38 further injuries caused with the knife, some of which were deemed life-threatening and required hospital treatment and surgery."
She told the court that Hanley did not meet the criteria for dangerousness - which would have elicited an extended sentence.
Hanley was jailed for 16 years.
He was also banned from entering Shoreham and a restraining order imposed.