Lady Forsyth, 59, is speaking as Sir Bruce, 88, continues to recover from keyhole surgery after a fall last year.
The fall caused two blood vessel swellings, known as aneurysms, which could have been fatal if they were left untreated.
Sir Bruce had been too unwell to attend the funerals of Sir Terry Wogan and Ronnie Corbett, which happened earlier this year.
Speaking to You magazine, Lady Forsyth said: "He has a bit of a problem moving, but we still laugh and talk.
"I pray, I believe. The main thing is that he's doing well. The pain is more emotional; sometimes we cry, but mostly we laugh.
"He's the man I fell in love with because his brain is there.
"Some days are better than others. On the not-so-good days, he tries to rest."
Sir Bruce Forsyth's parents were members of the Salvation Army but he himself has never spoken publicly about faith.
