"I think there were very strong positive and negative expectations when I started," he says.
"I think...I know I disappointed liberal and I didn't exactly reassure the conservatives either.
"And, looking back, I realise it was...hmm...I didn't make a very good job of it in my own eyes."
Dr Williams says he was confronted with the need for a lot of discernment and maturity, which he didn't always feel he possessed. But he always considered unity to be paramount in his work.
"I felt all the time that there is, at the heart of it, a calling somehow to keep people at the same table...literally at the same table.
"That has to be a really, really important thing," he says.
"I know some thought I then sacrificed principle for the sake of unity, but I found it difficult to say to them clearly, well, unity is a principle, and not just walking away...Because that mattered to me, I suppose I just found it difficult sometimes to take the clear action, one way or another, which people wanted."
He says it angered and frustrated him, and that there were probably quite a lot of kick marks on the furniture at Lambeth Palace.
He had had to apologise to his daughter, explaining to her: "You do realise that the reason that I shout at you sometimes is because I can't shout at the Bishop of Nigeria."
The Lord Leslie Griffiths interview – a series of five discussions with influential Christians – will be broadcast at 2pm on 25th October.