Weights: How to become more consistent?

I started lifting weights this week. As I was planning out what I was going to do, I thought about the fact that in the last 2 years I was never able to keep my weight lifting on schedule. I think I might have figured out why.

When I pulled out the paper that listed all the exercises from my training program, I remembered that it would take me about an hour to finish the workout. I think I need to adjust the plan to be in the 25-40 minute range or perhaps even shorter.

There have been times that the workout didn't happen because I didn't feel that I had an hour left in my day. So instead of doing part of it, I don't do any of it.
Then there are times when I couldn't bring myself to do the workout because I knew that I wasn't going to be able to stay strong through the whole list of exercises. So I'd put it off for a day when I might feel better...

It seems that I need to create a plan that feels much more "doable". So that I'm less likely to skip it.

Well right now, because of the marathon training, I want to take it easy on my legs. I'd rather do too little than too much seeing how I keep injuring myself preparing for marathons. So I've created a couple different workouts and they only take about 30 minutes.

One is all upper body which I'll do 3 times this week.

The lower body I think will break up into 2 lists.

One will be exercises that I can do at home.
The other will be a list of things I can only do when I'm at a gym.
This way, when I'm at the gym (not often) I'll only be doing exercises that I can't do at home, making the most out of my time spent there.

I also need to come up with a short list of lower body, at home exercises that I can do after a bike or a run. It may be that I need 2 lists that I alternate between. The point is to get the weight training into the schedule.
I had always been thinking about weight lifting being on the schedule twice a week. Breaking it up like this will probably mean there will be weights 5 days a week. Let's see how it goes.