I'm a believer in efficiency so I try to incorporate exercise in general tasks. For example, since I love to stand in the soothing pounding and warmth of the shower I stretch that time a minute by doing 20 toe ups for strengthening the calves. --and then cool down with cold to wake up and start the day. Lunging while putting on deodorant or brushing teeth also works. Call me wierd but slowly building metabolism!
I am now counting the exact amount of reps I do for each exercise. I stop an exercise when I start using poor form due to fatigue. This is both motivational as I try to beat my number and it keeps me using good form which prevents injury and maximizes the benefit of the move.
We all make goals like getting to the gym 3x a week and then life happens. I would feel like a failure. One day I went on the strength exercises of SP and picked out the easiest ones I liked. Enough for ten minutes (not many when you include stretching after). Voila the fallback plan for success