Well I am probably a bad person to add my thoughts here since I am on a perpetual roller coaster of on and off plan (usually it's one extreme or another).
BUT I will say that when I am doing well - and what I see working out for me long term for the future - is to budget the time I need to: plan, shop and prepare for each week. That means looking at what I already have on hand, planning what I
want to have on hand, procuring what I need from stores, markets or gardens, preparing whatever I can in advance (washing and/or cutting up veggies and fruits, cooking steel-cut oats/beans/whole grains and refrigerating or freezing them, boiling eggs, whipping up a soup or salad that keeps or a baked casserole of some sort) and then writing out the plan for the week so there is no thought involved.
The "no thought involved" part is critical. If I have my plan written out it is much more likely that I will make on-plan choices. I have a bad habit of waiting until I get too hungry and then "deciding" what to eat
It does take some time but at least the time is in one big chunk (say a Sunday afternoon or evening) and I have fine-tuned my checklists and lists of ideas. I keep a weekly planning document that lists: everything I have that I need to use (fresh stuff), what is residing in the freezer and pantry that could be used, what I need to purchase and a whole bunch of ideas for meal-planning and some copies of planned days that I think worked out really well. Also I note if some days will have particular challenges, like on the road or a dinner/lunch out.
Anyway, all of this planning ahead - for me at least - has become like a game and makes it fun. What is
not fun for me is winging it and getting too hungry, and flipping a switch that opens the floodgates into mindless binge-y grazing.
I'd also like to hear more tips & tricks...