One more time....but will be last

I am new to MFP, hence the introduction duh. I know it is time to do something new, something that makes sense. Basically to lose weight is a calorie deficit and to gain just the opposite. Also no one gets healthy eating a salad nor does someone gain 100 pounds by eating some pizza. I know all this but putting it in action has been a different story. Did well on WW a few years ago, journaling was the key there, but decided to take off for the holidays, could never get it right again. A few sputters here and there, but could never get anything going again. I do have chronic back issues and been on medications for a few years, but after a change there I hurt everywhere, knees, feet and of course back. I do not want to live like this anymore, where what little energy I have goes to work and everything and everyone especially myself goes without. So here we go again.................