It just takes practice. Back when I played bass in a band it always took practice to learn new songs, even songs that looked/sounded "easy". Granted, some songs took less time to learn than others. Sometimes it took something really simple to progress in a song. That thing was to just relax. Your fingers should know where to go for most chords, but if you're concentrating too hard on the chords, your fingers get a bit "stupid". But if you relax you may have some startling results.

I know that when I'm not actively concentrating on practicing chord changes they tend to go easier.

It works for me, maybe it'll work for you too.