How do you approach workouts?

Different workouts serve different purposes. It all depends on the workout, time of season, where you are in training cycle, etc. Judgement call on the day.

Rule of thumb is to leave something left in the tank for most workouts.

A little off topic, but I try to approach each workout with the mentality that I'm going to run swift and controlled, and push close to the edge. I try and make every workout an opportunity to get better, and I visualize elite athletes that have good form and run relaxed. That helps me get in a good mindframe to tackle workouts. I never kill myself, but you have to go up to the line occasionally to get a feel what your body is going to endure in a fast race. It's an approach that I've learned as a mid-20's local-type runner, that I didn't have when I competed in high school.

I always reminded myself what my goals were and how each workout fit in those goals.

So I wasn't going to go out and bash an easy run if it didn't help me in that regards.

I think both have their uses. Obviously you can't always be going to the well in workouts but I do think there is a time for extremely hard workouts. By pushing your body to the absolute limit you provide a stimulus that prepares you for races and allows you to reach a level of fitness higher than what could be done with less than all out workouts. Of course these workouts will mean nothing if you cannot recover and that is where the real challenge in training comes in. You want to push your body to the limit of its performance without going over.

leaving something in the tank is more about the head than it is about the body, assuming that a person allows for ample recovery. trying to go 100% too often wears down your mind, and people who do this tend to crumble when it really matters. i think that a person has to push it to the max in workouts from time to time, especially if competitions are few and far between. max/new limit type workouts need to be scheduled rather than being allowed or forced to happen. pushing the body to new limits in practice should be followed by exceptional recovery. adaptation and improvement come from rebuilding and recovery.

I think that's a good point. I brought this up mainly because I coach a lot of kids who are very neurotic about their workouts and who are constantly running faster than the prescribed times because they feel like they are not working hard enough otherwise. My own philosophy is that you should finish most workouts feeling like you could do more, and that if you finish a workout completely drained, falling on the ground vomiting, etc. than you probably ran too hard. Certainly there's a need for one or two gut-busting workouts, but as mentioned above the recovery time required for those efforts makes it hard to have them as a regular feature of your training cycle.