Workout! Set your alarm a little bit earlier, then spend some time with your coffee before putting on your workout gear. It seems counter intuitive, but if I don't sleep well the night before, I always find just getting out of bed early and getting a workout in makes me less tired throughout the day!
I second the idea of yoga for desk workers, I'm always looking for a way to stretch it out during breaks at work. But my desk isn't in the most private area, so maybe simple stretches that won't have me laying on the floor would be good!
Also, how about a yoga roundup for a great flow that is easy to remember for a post-run stretch? That would be awesome!
I totally agree with the feedback you have gotten here! Make sure you're challenging yourself -- workouts should always feel hard, but not so hard you're breaking form. Aim to be lifting a weight that will challenge you for the last rep or two (feel very hard), but won't compromise your form. Remember that if you're compromising your form, you're more likely to be injured.