I tell myself in the mornin that I am going to the gym when and then when is time, I find a million different reasons not to.
That is cognitive, and you need to change your gym habits into behavioural. When you can't get self-motivated for gym, you do it by repetitious behaviour. You set a time, usually first thing in the day. You get up earlier, you go to gym, then you do your day. That is the best method for exercise, otherwise if you have a tough day, are stressed, any number of reasons by the end of the day, many a person then puts off exercise. Suddenly, their fat, depressed, stressed and wondering what the hell went wrong in life.
Gym is behavioural. I wakeup in the morning, I get in my gym clothes... and whilst my timing for gym changes daily, I am self motivated to so it and when wearing my gym clothes, I go do it. I may do some computer stuff first, or I may go to the gym first... but I don't get distracted as I'm wearing the clothes and get myself out the door.
Exercise is behavioural. You have to have a routine for it. Some of us enjoy exercise and thus it is more enjoyable than a choir, as many see it. I enjoy it... but I also understand the choir mentality. When something is a choir, you do it by repetitious behaviour, routine.
You also have to do it slowly. If you want to run 5 mile, but don't run and are completely over-weight and unfit, then you start walking using incline, or walking up hills. As your fitness increases and weight decreases over the months, you then start running half a mile each day for a week. The next week you increase it to three quarters a mile for that week, then the third week you run one mile each day. You keep very slowly increasing your distance, repeating it for a week, increasing the next week. Your fitness continues to increase, your weight decreases, and your exercise becomes easier with each week.
Months later... you're running 5 mile, or your goal distance, on a daily basis. Thinner, healthier, happier and able to eat some yummy foods here and there without weight gain due to the amount of exercise you're doing each day. When you get close to your goal weight and exercise goal, you decrease your exercise to include rest days. Then there is life and some days you just can't get to your exercise... but they should be few and far between, like go away for the weekend. You can still put exercise into holidays, by being more active, doing things that are more active, that you otherwise wouldn't have done.
Age is not a barrier to exercise. With age a person becomes easily over-weight, sore muscles and such.... because of stress on the body. Lose it all, suddenly you're moving like you didn't think you could and by using muscles your joints become more secure, stronger, thus can be more active throughout older age. You just keep your heart rate at the maximum for your age, no further. As you get fitter, your heart rate will drop, allowing you to increase intensity a little more, until you reach a peak for your age and fitness level.
If you're carrying lots of weight, allow a year or two for all this. If not, but your fitness / age is the impairment, do it slowly and build up over months, so by the end of a full year at it your fitness and physical well-being is where you want it to be.
