The key is:
get a routine and stick to it; we all like to have a routine, it gives us structure and helps us feel calm.
I'm not saying this is the way to go for everyone, but this is my routine:
Monday, Wednesday and Friday, I drag the exercise bike into the living room in front of the TV and stereo.
I either put on some music, or put on the TV, and watch something I have recorded or a DVD.
I do 25 minutes on the bike, at an average speed of 20 km/h.
I also do 100 abdominal crunches.
Don't get me wrong, I hate doing my exercise, it sometimes hurts, and its' a pain in the butt to have to get the bike out and do it.
I also make sure that when I do my exercise, I put on a pair of lycra shorts (not bike shorts, but just above the knee swimming shorts), and a sleeveless t shirt - it's an exercise shirt, and it wicks away the perspiration.
If I didn't wear these, I would not persevere, as the chaffing and friction and distraction of wet clothes would prevent me continuing.
I also go to the pool every weekend, and do 300 squats and 40 laps.
Again, I hate doing it, but I take my wife with me, and pop her in the pool first.
If she can commit to swimming every weekend - and I have to lift her out of her wheelchair and put her in the pool to do it - then who am I to say it's too hard and I don't want to do it?
The problem many people face is they don't feel motivated to exercise, and they want to feel "in the mood" to do it. Guess what; if you wait until you feel like it you'll never do it. The only way is to do it even when you feel like crap, when you feel like you'd rather go to bed, or you just can't see the point.
Why? Because when you do, you'll burn off the stress, the hormone imbalance that feeds your depression and anxiety, and you'll get your body in better shape in the long run.
That and you'll eventually feel as fit, if not more so than others your own age.
You don't want to be in your 40's wishing you could go back to having the body you had at 20 - you can't do that, but you can work on having the best body you can manage to have for your age.
You don't have to be a gym junkie, or even go to the gym, you just have to make an effort when it feels like there is no point, because otherwise crap is as good as you're going to feel.
I'll never be an Arnie Schwarzenegger, and I may not even get rid of my spare tyre; but at least my body can usually do what I want it to, and I can feel there is some hope for keeping the anxiety and depression from crippling me, and that's got to be worth the effort.