In my experience, two things help a lot for consistency. One is finding an exercise you like- even better if you don't consider it exercise! Like, if you love hiking, then hiking won't feel like exercise. Or dancing. Something like that. The other is to get friends that will do it with you. I have a friend, for example, that will hike in ANY weather. Zero degrees? She's game. If it's under 20, I don't really want to go that much, but she'll ask and I always say yes. So she motivates me to go. (We live in Alaska, so we have the clothing for it, it's just a matter of motivation.)
I agree that something like dancing that doesn't feel like exercise would be helpful and having a friend to walk or exercise with could be a motivator. I find time was always an issue for me so doing something like strength training exercises (squats, push ups, plank, crunches etc) that all total took 10 minutes or less was helpful and better than nothing. If you have access to a treadmill, scroll Facebook or play a game on your phone while walking on the treadmill and time flies, you can do a 20 minute mile and only feel like it was 10 minutes.
I have never found a regular form of exercise I love, or even like (there are some activities I enjoy, but they aren't going to happen 3 times a week). But I have found a way to incorporate exercise into an activity I enjoy and am happy to do daily. I have a plank on my treadmill and I walk while I browse the web (like now!) or play some simple games. In fact, in recent years I've gotten involved with a couple of games simply because I knew they would make the time fly on the treadmill. In a perfect world, I would incorporate lifting and cardio, but I haven't found a way to make that happen and walking 10K steps a day is a lot better than nothing!
I love group fitness as a form of exercise, I know it's not for everyone, but there are so many different classes to go to! Once you get a membership you can schedule it in and go to the classes on a routine! Then you even get to make connections with the instructors and other people who go as well. On days when I am struggling with motivation I make sure to try a class.
What helps to motivate me is remebering that feeling you have when you're finished with a workout! You know that feeling when you can actually feel your blood flowing and your lungs feel invigorated and you just feel plain accomplished? When Im lying in bed considering sleeping in rather than working out, i think about that amazing feeling and how great it is to start my day with that! That USUALLY does it for me!
You don't say much about what you are trying to do or what is causing you to derail from your plan, but here is some general advice that might be helpful. I agree with the general "find something you enjoy" approach. But even more important than that, I'd advise asking yourself three questions:
1. Is there a better time in my schedule to fit in exercise? If you already find it hard to wake up in the morning, for instance, and now you're setting your alarm an hour earlier to exercise, maybe morning workouts aren't the place for you to start.
2. Am I biting off more than I can chew? If you're not used to regular exercise, ask yourself if what you have chosen is too challenging, and maybe start lighter.
3. Am I being kind to myself, or am I thinking this is all-or-nothing? If you skip a day, do you tend to think, "well, I blew it, I'll never get used to this regular exercise thing." Don't beat yourself up about it. If you skip a day, then just do your next regularly scheduled workout when it's time.
When you find something you enjoy doing (at least for now), don't try to do too much, and don't try to give yourself a complete personality transplant overnight, you might eventually find that you like the way the exercise makes you feel, and it might become easier over time to stick to your plan.
I agree with EagleRiverDee. You must find something you enjoy doing so it doesn't feel like exercise.
I have always been athletic, but after college, I fell off the bandwagon because I didn't know what else to do without team sports. I missed the sports competition and for a long time there was a big vacuum in my life. That made me feel kind of depressed.
Then years later I found out about tennis leagues, and I really got into it. Tennis is a very fun and addictive sport. When you play it, it's so much fun, it does not feel like exercise. You can play at any age, singles or doubles. And if you like athletic competition, I really recommend you give it a try. We league players play or practice many times a week (yes, it's addictive). And the more you play, the better you get. You also get too make new friends, it's very social and fun.
Oh- one more thing on the lines of Carter's "Am I biting off more than I can chew" suggestion- definitely do baby steps. For example- I like to do some pretty hard programs such as P90X. But when I start them, I NEVER do the whole thing at first. So let's say they want you to do 25 reps? I do 10. Or lets say it's a 1 hour program of cardio? Maybe I'll do a half hour. That first week or two, I take it slow. Because nothing derails a program faster or discourages you more than an injury or being so sore you can barely move. That's no fun. Ease your way into whatever program you're doing.
Final thought: Do SOMETHING every day. That has worked really well for me. I will do something. If it's 10 minutes or it's an hour, that's ok. I listen to my body. It might be a quick walk around the block. Or it might be an intense 1 hour of lifting weights. Do something. You'll often find that you didn't feel like doing it at all to start with and had to force yourself to start (giving yourself permission to quit in 10 minutes if you hate it) but once you're moving, you keep moving.