In Boston Brass master classes I used to hear Chris Castellanos mention a really great tip to get kids to practice more and more frequently. When he was a student, he was taught to keep his horn out of its case on his bed each day.
He shares that there was only so many times he could walk past his horn lying there, ready to play, without picking it up and at least playing a few notes on it. He found that he played a lot more if it was staring him in the face than if it was in its case in the corner of his room. He also has found that it works for his students too.
So leave that horn out where it is very hard to ignore it!