Jacqui Clancy and her 77-year-old father, Gerry, have been isolating together since March.
Mr Clancy, a former Navy veteran, struggles to understand the pandemic because of his illness.
Ms Clancy believes many carers are really suffering and will worry about a six-week lockdown after Christmas.
Speaking to BBC Radio Foyle, she described how prolonged periods in lockdown have affected them both.
“It has got harder, my mental health has definitely been affected and family relationships have definitely been affected,” she said.
“He has lost a bit of himself and I, along the way, have lost a bit of myself.”
Jacqui and her father went into isolation more than 10 months ago for health reasons.
She said there is a general sense of optimism among people she knows that things will get better next year.
But they are struggling.
“Although there is light at the end of the tunnel, I also think the fear of this further lockdown is going to affect a lot of carers over this Christmas period, me included, and it is scary to think what next,” she said.
“I don’t know if 2021 is going to start any differently.”
Ms Clancy said her father has always been sociable and loved seeing different faces.
However, since the lockdown in March his condition has deteriorated and he has “lost his mobility” and “lost his friendliness skills”.
“He is here all day. There is no function to his day. He can’t tell the difference between day and night,” she said.
“I have been sleeping on the sofa for the past eight weeks.”
A new six-week lockdown in the North of Ireland comes into force at one minute past midnight on Boxin Day, December 26, with Stormont ministers reviewing these measures after four weeks.
Ms Clancy believes the lockdown could be detrimental to her father, who thrives off of human interaction.
“It is scarier now, there has been a big shift in mood, community spirit and people have hunkered in and it certainly isn’t good for my daddy,” she said.
“It’s sad to think there are a lot of carers out there who are really suffering right now – especially at this time of year.”
Ms Clancy said that even if a Covid vaccine is effective and the situation improves, she will never be able to get back the time lost to the pandemic.
“From my perspective, I think we have already lost so much.”
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