I agree - something you can and will stick with is BEST!
I took up yoga in 2004, and have LOVED it. I also do tons of walking and hiking, just because I like it. Lately, I have worked on ramping up the speed and distance. Because I have plateaued before at about 180lbs (went from 180lbs to 192lbs last year, blah!) I am currently doing free weights and body weight exercises like lunges, pushups, squats 5 days a week. I am unemployed right now, so I have been taking the opportunity and have been doing about 40 minutes to an hour of free weights and bodyweight exercises 5 days a week, followed by either one or the other or both of yoga or walking. Feels great, too! The goal is to build some serious muscle so when I hit 180lbs, I have more muscles to help me slam through that plateau. As I get lower, I will swap to doing to free weights and such 2 or 3 times a week, yoga still 5 or 6 days a week, and add in some kind of sweat-inducing cardio to help me motor down to a low weight. If I become employed, however, that all gets cut back and I just do SOMETHING every day but Sunday. Because I can stick the "Something every day but Sunday" plan. Sticking with it is what matters. You can do it!!!