You're human, so don't worry about it. Anyone who lives like this, will have at some time questioned it. It's normal. You try to understand, to justify, to level with yourself it's worth it, especially when you see old guys with skin like a Rhinos butt, tottering along having a smoke, then you hear about guys in their 20's, having heart attacks playing sport.
It's not logical and it doesn't even sometimes make sense, but life's a gamble. The question is can you gamble on the do nothing option and hope it works out? Do you gamble on a bit of both? Exercise but drink Beer or smoke as well? Or do you gamble on the stop indulging and get seerious about the future option?
We can't predict the future, but we can try to alter it's outcome somewhat, so you can in most instances load the dice in your favour. You will always have to play lifes game, for as long as you're permitted, but it's up to you how you define your own rules.
Don't think about what you hope to happen in the here and now, think about what you hope not to happen in 30-40+ years from now. You can make changes now that will help later in life, but if you start then, they will be that much harder to make happen and almost certainly won't happen to the same exent, so procrastinating would eventually be selling yourself short.
If you truly believe you're worth it and I am convinced you are, then you can see your own self worth and that is a big motivator. You have the power NOW to change things for the better and that is why you ARE BRILLIANT and you ARE capable, because you're just beginning to tap into your own capabilities.
When you give it time, patience and learn to be more understanding and forgiving to yourself, you can then make hings a little easier for yourself. The only motivation you need is to realise that the only thing stopping you from succeeding is you, and that you don't have any barriers to physical success, except those you make for yourself.
So kepe going and no worries okay
You CAN do this, just keep trusting in your head and heart to guide you. I KNOW you're worth this, but you need to feel it 100% like I do. I KNOW you can do that as well and once you feel it, you'll find it all much easier to continue with
You have a beautiful personality and a great heart. Let them shine and don't be afraid of anything, except losing the will to continue. That alone could be enough to keep you on track.
Chin up, be strong and GOOD LUCK.