You're not alone -- so many of us are fighting this battle and struggling with it daily and we're here to support you.
If I'm reading you right, I think what may contributing to the overwhelming feeling is you're looking at this in the biggest picture possible, your whole life. It's sounding like you think you'll either get to be healthy and never eat cake, or eat cake and be heavy and unhealthy.
I think there is a happy medium. I don't think we're always able to find it right away. Shrink your picture. Look at whatever time frame feels least overwhelming to you - a day, a week, a month - and go with that.
You may not be able to have a piece of cake now (I also am steering clear of treats because I don't have a lot of control myself) but that doesn't mean you won't be able to your whole life (I think no treats forever would make any of us miserable!). I think the answers become clearer to us about our personal limits the further we go in this journey.
So keep going! Don't give up! It will feel better to battle this, even if you slip up, then to just give up.