The Jews who left Egypt didn't make it into the Holy Land. They couldn't believe that Hashem was strong enough to conquer so many powerful nations. But even though they didn't make it, their children did, as is says "and your children who you said would be plundered, they will come there, and they will inherit the land".
However, it is important to realize that the children who entered Israel still entered on the shoulders of their fathers. Even though the fathers hadn't finished their jobs, they had already accomplished a lot just by "leaving Egypt". It wasn't in the merit of the children alone that they made it into Israel. This is an important concept to understand. What we don't finish fixing in our life-times is often passed on to our children to finish. There is no escaping it, the job must be done. But the more we do of the job that we were given in our life-time, the less our offspring will need to struggle down the line.
"Stopping the bad behaviors" is analogous to leaving Egypt. And being truly "free" from the addiction, with a clear mind and holy thoughts, is perhaps analogous to entering the Holy Land. Often after leaving Egypt, one still finds it hard to trust enough in themselves/G-d that he will one day make it into the Holy Land as well. However he should know, that the simple fact that he has left Egypt behind makes him worthy enough that G-d will help - either him or his offspring, to merit "entering the land of Israel" one day, and achieving true purity and freedom.
Every time we say "no" to our Yetzer Hara, we are in essence saving our future descendants from these same struggles. And no matter what we accomplish at the end of the day, we must always remember and believe that none of our work goes to waste.