Westley was relieved of his duties at the Lancashire club in February after picking up just one league victory in 11 games.
The former Stevenage boss spent 13 months with the League One club and felt his dismissal was harsh, bearing in mind the financial situation.
He told the Daily Mail: "Preston never got to see Graham Westley at his best.
"I can remember saying 'Graham Westley at Stevenage would do this or that' on several occasions, as I fought for some empowerment.
"It makes me giggle to think that there is a perception that things 'went wrong'.
"The expectation of promotion that the club set for this season was unrealistic in my eyes, bearing in mind the size of the change, the wage reduction and our budgetary position.
"I felt hamstrung. I knew the answers to problems but I wasn't being allowed to solve all the problems."
Westley continued: "Short-term pain is necessary sometimes. It was necessary at Preston.
"I stopped a sinking ship from sinking further but I didn't get to drive it hard on the right course."
He added: "I am good at looking in the mirror, admitting errors and getting better. I feel better than ever right now."