First, every significant other is different. I can only say what works for my wife and myself.
Having said that…
My wife loves the outdoors, but in a much different way of enjoying it than myself. Where I love to walk all day, she loves to get up early, enjoy camp then hike..get in a little earlier and take in the atmosphere when ending the day.
And after four years of going to grad school and working full time, frankly her exercise has taken a back seat.
So, we have been car camping more so than anything in the past three years.
We took our first backpacking trip together in three years recently.
I took most of the gear, made a great backcountry dinner, kept the mileage AND elevation gain low and picked a trip she would like.
http://www.pmags.com/buffalo-peaks-saunter
I also have to learn to be flexible. We were supposed to go out together this weekend, but she had a busy week and the weather is supposed to be crappy. Looks like an easy day hike instead Saturday and perhaps something more challenging by myself this Sunday.
So it goes.
(And next weekend is a 50-60 mile solo trip!)