Sotherton retired from the heptathlon in 2010 and targeted a 4x400m relay place at August's World Championships.
But, after not taking part, she lost her UK Athletics second-tier "podium relay" funding this month.
"I'm not angered by the decision, I don't feel it was unfair," Sotherton, 34, told BBC Radio 5 live.
"I had my funding knocked off because my performances in the 400m weren't good enough."
The athlete, who came third in the 2004 Olympic heptathlon, says she had already decided to return to the multi-discipline event before her funding was cut because she found training for the 400m "laborious".
Sotherton said: "Back in the summer I realised I wasn't really going to be funded for 400m and I was thinking of probably retiring.
"I'm one of these people who, if I don't train well, then I don't perform well. I wasn't enjoying my training, so it was like a vicious circle.
"I just found it so boring. It's so laborious, just running, running, running, running.
"The mental stimulus from doing so many different technical aspects of the event (heptathlon) makes it more exciting.
"There's always something new to learn every day. With running, there isn't - and my hat is off to everyone who runs because it is pretty boring.
"I made a decision back in the summer that, if I can prove my body could hold up, I would go back to heptathlon, rather than retire."
A visit to a doctor in the Netherlands revealed that the Briton's previous back problem had improved significantly and she decided to return to the heptathlon in July - with the funding announcement then made in October.
Sotherton added: "I felt I had no cause to appeal because my funding was based on the 4x400m relay. I never went to the World Championships because I took myself out of that selection.
"I hoped they might still fund me for heptathlon but realistically I knew that wasn't going to happen - I hadn't performed since Beijing (2008) in a heptathlon."
Sotherton must still achieve the qualifying standard to have any chance of making the Great Britain team of next summer's Olympic Games.
The Olympic 'A' qualifying standard is 6,150 points, comfortably below Sotherton's 2005 personal best of 6,547. She scored 6,517 in her last heptathlon in 2008 before heel and back injuries forced her withdrawal from the multi-discipline event.
"It's something me and my coach put a lot of thought to," she said. "It hasn't been a nightmare. My dreams and aspirations still remain the same.
"I'm still training just as hard. I've been in training for a month and I'm thoroughly enjoying it. It has rejuvenated my feelings for the sport."'I wish I could take on Ennis' - Sotherton speaking earlier this year