"To play international rugby you have to be absolutely committed. You have to make sacrifices and do all the extra stuff in training and preparation to be right," the loosehead prop, 34, said.
"I've always tried to do that throughout my career and playing for Scotland has meant the world to me.
"But the minute there is the possibility of it feeling like a chore... well, that's the slippery slope for me and I would never want to do anything that would either devalue the Scotland jersey or anything that I've achieved."
Nicknamed Chunk, Jacobsen made his Scotland debut in 2002 and his last appearance came as a replacement in the 51-22 defeat by New Zealand on November 11.
Scotland were beaten 21-10 by South Africa at Murrayfield last weekend and next face Tonga in Aberdeen on Saturday.
Meanwhile, South Africa lock Eben Etzebeth has been cited for making contact with the "eye or eye area" of Scotland fly-half Greig Laidlaw.
The alleged incident occurred in the second half of the Springboks' 21-10 victory over the Scots.
Etzebeth, 21, will appear before an International Rugby Board disciplinary hearing on Tuesday.
South Africa play England at Twickenham on Saturday.