I know all about this problem....hating to end the meditation 'cuz it was "just getting good", etc.
Here's the solution I found: take it with you. As you rest, as you get up and interact with the world, you needn't reconstitute into something noisy and superficial. Be your silence through the day.
If the meditative state means feeling dull-witted, sluggish, oblivious, or otherwise unaware, something's very off. Your silence is your awareness. And your awareness is sharp (just not noisy or graspy). You can be sharp driving, talking, walking, doing anything, and be 100% in your silence.
See if that helps.
The other tip is that, like eating or sleeping, the precedent you set for yourself in terms of sched becomes habitual. So if you meditate every day at the same time, and do it for precisely 20 minutes, that's what you'll crave and that's how it'll work. You tend to overshoot only when your body hasn't been conditioned to a routine. Get into the groove, and it all takes care of itself.