The hooker said the coaching regime which replaced Stuart Lancaster's team kept them on their toes.
The 30-year-old New Zealand-born hooker -- who has proved an inspired choice as captain by coach Eddie Jones despite a poor disciplinary record prior to that -- added he didn't know whether he would be a part of it.
He said the coaching regime -- headed by 56-year-old Australian Jones -- which replaced Stuart Lancaster and his assistants after the 2015 World Cup debacle kept them on their toes.
"It has been a hugely successful year, it has given everyone involved a taste, and everyone on the fringes something to push for," said Hartley.
"It's an aspirational group to be in. People want to be there.
"But we've drawn a line under last season and we've already sat down as a team and said, 'What do we want to achieve in the next year?'
"The challenge for everyone, the coaches and the players, is we've all got to go away and improve.
"If we all improve, then collectively when we come together we will be better.
"It's just the beginning of what I think will be a really good period for England rugby and I'd like to be a part of that going forwards, but the reality is you might not be."
Hartley, who has served five suspensions for disciplinary infractions, said he has been held to account over his performance in training since he returned after a lay-off with a back injury.
"The thing with training now is they have GPS, and that doesn't lie," said Hartley, who faces stiff competition from Saracens' Jamie George.
"I didn't hit the expected levels one day and I got told, 'Not good enough. You should be leading by example.'
"So the next day, you're thinking, 'I need to be exceeding expectations.' Eddie is always asking questions, always pushing me, saying, 'Not good enough, you need to train better,' sowing the seed of doubt in your head."
Hartley, who has never lost when he has been England captain winning all nine under Jones and drawing one of the Tests when Lancaster was coach, said despite the seeds of doubt he enjoys a very good working relationship with Jones.
"We talk weekly, sometimes daily," said Hartley, who will skipper England in the upcoming November test series with two-time world champions South Africa first up next Saturday.
"There is always contact with someone in the set-up, not over the top, in your face, but regular feedback on your games, off-field matters, what do you think to this or that idea?
"You always have that seed in the back of your head, thinking about England, thinking about the bigger picture."