I have always found the opposite move G to C more difficult. I tend to go through all the chords I know very slowly during practice checking that the fingers are fretted correctly and that the strings ring clear with both a pick then a strum. Then I practice chord progressions gradually increasing speed as i get better. The more difficult changes i spend time ghosting slowly with fingers hovering over the chord position before setting them all down or as near as damn it. The way i cracked the G to C was to focus on getting one finger from one chord to the other i.e. the the ring finger and the others just seem to follow. As everyone points out though it is about structured practice. Small daily progressions slowly build and when you look back over a year you are amazed because you are now doing routinely things you thought were beyond you. If you enjoy the learning and are prepared to practise you will get better. Happy playing and good luck.