Welcome,
When I read your subject I though "well, hopefully get off the rollercoaster at the bottom

"
If you've tried and failed to follow specific plans in the past, maybe that's not for you? Following specific diet regimes works really well for some and really poorly for others.
Personally I know that I will fail on anything that leaves me hungry or forces me to permanently give up anything. So I've found success in simple calorie counting online. I have a target range for calories (and also rough goals for fat/carbs/protein), and I work each day to be around that target. If I find I'm way off from that target (high or low) I'll adjust. I count everything, even horrible cheat days, and plan ahead for things wherever possible.
Regardless of what you choose to do, the fact that you have rollercoasterd a lot in the past is actually very useful! It means you have a LOT of information about you, your behaviors, what works, what trips you up, what's liveable, and what is a temporary solution. One of the first things I did when coming up with my own plan was look at personal weaknesses/barriers (ex. I travel a LOT) as well as personal strengths/assets (when at home I can schedule gym time whenever I want). Then build behaviours into your plan that utilize your strengths and specifically target your weaknesses.
I am actually typing this from a hotel room on the road and this is fresh in my mind, because I just ate some brown rice sushi in my room that I picked up in the grocery store (one of my travelling behavior changes).