It may or may not happen to you. This feeling of sudden curiosity with music and saxophone, then eagerness to practice (sometimes frustrated you couldn't practice that day), then reaching a goal or achievement (for whatever the case), then CRASHHH... Meaning, all of a sudden there is no adrenaline or anticipation of what more to learn and excite me.
Hopefully this 'quiet' period will run over soon. Deep deep down I feel I need to practice and not waste the effort I've put in. But whenever I see my saxophone, I'll say "Tomorrow lah, too tired today". So, doing practices alone is quite boring. Find your means and ways to spruce up the activity. DON'T GIVE UP...