on balance
Moderation is hard. If you are trying to get to your goals and you've been more unsuccessful than successful so far, binary thinking is a better approach for you in the short term.
A sustainable, balanced lifestyle is the dream. But if you had been doing that, then you wouldn't be here today. It is because you sat too much, ate too many chips, drank too much juice, inhaled too much biriyani, watched TV instead of sleeping etc that we are having this conversation.
reinforce the goal daily
You wake up today and tell yourself that you will go to the gym, or if that fails, you will go on a walk. You make a decision that you will not eat sugar today. Done!
Stick to the plan for today.
Tomorrow is another day and you can set your goal and reinforce it in the morning.
If today is a special day (birthday in the family, seeing a buddy after ages etc), then you can plan that goal-setting in the morning accordingly. You will eat a gargantuan salad for lunch, you will get your workout in and then you will head out and have fun and eat lots of cake and drink lots of beer.
And tomorrow, you will come back and go to "NO" to everything. And do that for a few days to balance out the excesses of that special day.
just one bite, please ...
The issue arises when you tell yourself it is just one bite of cake, or just a few bits of chips and what-not. You are not skilled enough or responsible enough to do that. So, just stop with it!
These things add up. More than you realise. The only other way is to maintain a diligent food journal about all of it and ensure that they don't actually add up.
And you are measuring what you need to measure daily/weekly/monthly right?
If you are doing enough of the right things, then the measurements will move in the right direction.
The issue with a bite of cake here, a piece of candy there and all that is you think you are doing enough of the right thing but the scale is not moving in the right direction. And you blame me (or your gym or whatever) for not being good enough. When the issue is simply one of you not being honest with yourself about your actions and goals.
no moderation for you
The first principle is that you must not fool yourself and you are the easiest person to fool.
– Richard Feynman
You (obviously) are not lying intentionally. You (obviously) are not trying to fool yourself. But you are. And it is much easier to blame someone else than yourself when results are not where they should be.
So, just stuff it with the moderation game. You will get there someday. But maybe not today.
For now, binary thinking works. Yes or No. No means no. No does not mean "a little bit".
Do what you need to do. Measure. Do more/better.
You'll get there. It might just take much longer than you think. But you will get there.