What helped me the most was singing and conducting music. I've also had gotten great results from tapping the beat of the music I'm working on while speaking the rhythm on a a single syllable (like 'ta'). You can do any of this with or without a metronome (or use the metronome periodically as a guide). Trying to find a fun way to work on time can also stretch the mind some and be...fun. Time, like sound, intonation, style, etc., is just one more piece of the whole picture and absolutely it can be improved. It's a lot like being in a play - when do you say your lines and how quickly? It may help to simplify the process for yourself somehow so that it doesn't appear mysterious.