You training rides need to be harder than your group rides. And you need to do 2 or 3 solo training rides for every group ride/week.
Or find a slower group.
But don't forget things like staying aero if you are doing 15 to 20 or more mph up a hill. I still have a bad habit of sitting up while climbing at speed. But I'm getting better. If you have developed into a spinner going up hills, don't forget to shift to a higher gear occasionally to see if your legs have gotten stronger and can spin a higher ratio at the same cadence. That might save you some energy in the long haul.