The Toffees, who have been notoriously slow starters in recent times, burst out of the blocks this season and into the Premier League's top four.
However, a defeat to Reading and an inability to kill off a home date with Norwich on Saturday, which resulted in the Canaries snatching a late point, have led to David Moyes' men slipping out of the UEFA Champions League places.
A run of three wins in 11 suggests there is room for improvement at Goodison Park, ahead of a midweek date with Arsenal, but Jagielka claims morale remains high, with recent performances having deserved greater reward.
He said in the Liverpool Echo: "We shot ourselves in the foot a bit in the last few games. We've not kicked on when we've started games well.
"Against Reading in the first half we played as well as we have done all season. I had a couple of chances myself, the strikers had a couple of chances and so did the midfielders. But we never took them, and we came out at the start of the second half a bit sloppy, and before you know it we were 2-1 down.
"With the couple of injuries that we've got, the squad isn't looking quite as strong as it was at the beginning of the season, and maybe that doesn't help.
"But we're normally talking about not having many points at this stage of the season. We usually play for two-thirds of the season and forget the other one. So we can't get hung up on results."
He added: "We should have done better, but there's plenty left in the season and we've still got a decent platform to build on.
"If we were playing hopeless football and not getting anywhere near the goal, not making their goalkeeper make saves, then there would be bigger issues to deal with."