I joined a program 40 days clean, and im currently at day 37.  But I'm concerned, as with most kabbalas and deals I've made in the past, that as soon as it's over, often the day after, Its over, and I fall. Its as if the deal/program gave me strength, whether the deal was with the One above or even with a friend, but as soon as it's over, I tell myself, alright you did your part, this one fall will make no difference, and then comes the next, and then the next. As I'm reaching the end of 40 days, and to be honest, they haven't been that difficult, but I'm most concerned for after, the next week after, which will probably be the most difficult.
I'm not really sure where to turn, and how to navigate and set the proper guard so I dont succumb to the yetzer hara. He knows his time to shine is approaching, and he's been hiding out, strengthening himself, so the day I will turn off the extra security I had, the 40 day program, he can attack, as he always did, but this time I want to win the battle.

This is sadly one of the fundamental flaws of the count and one of the reasons I don't count but let GYE count for me. Try to not count to forty but try to keep being clean and use the number of hours, days, weeks etc as a little booster when needed. 
When you fell after your kabalos in the past what did you use? do you have access to porn or other stuff that would usually make you fall but only bc a kabalah you haven't, or is it just masturbation that you just fall once the extra bounds of the kabalah are gone?
What it appears like is that you are just using a kabalah to push it off and then waiting for the end so you can just do whatever you want.
This may work for others but for you it doesn't look it will last long term.
Counting to me always felt like your counting till your next fall.
It would help to know what struggles you have and what geddarim you have set up. and of course which of those gedarim appear not to work.

 Each and every day adds up, but only today counts
          Much Haztlacha!!

I feel for you man, I had a similar experience with the 90 day program, after hitting 90 days I fell a few days later. What I did last time was to start a new program, not counting more days but working on various related topics (GYE+ has many great programs to go through) and I felt that it helped a lot, you can also start reading the B of the G and have that be your "program", it may take time to find what works for you but I've found that this helped me. Also a big high five on identifying a challenging area! This is awesome for you, because now that you are aware of why you're falling you'll be able to devise strategies to combat the YH. Hatzlachah Rabbah! feel free to PM me if you want to be in touch further, and please keep posting to let us know how things are going during next week, and beyond.

40 days is great!!!
Simple question: Why can't you just make the kabbalah anew for the next 40 days?

Thanks everyone for the feedback. I fall because the extra geder of the kabbalah/program is gone, and thats what held me back, but without it Its like I feel no reason not to, like why not, just one time, whats going to happen.