"It hasn't been [easy] at all," Cotterill told reporters from his car as he left Fratton Park. "I have a great relationship with a lot of the people I've worked with here. It's been quite upsetting this morning.
"I needed to make sure I composed myself before I came out here to talk to you guys. It's been quite upsetting. I'd rather not elaborate to be honest, because I know I'll get upset again. Is that alright?"
Cotterill, a former manager at Forest rivals Notts County, said he had been "flattered" to be offered the role. "They're a fantastic club and from the time I knew about their interest, it was obviously flattering. I just need to go up there and see what they have to say."
The appointment is expected to be officially announced this afternoon.