The message of the video is simple: just because you are involved with one sin, by the rules of their religion, it doesn't mean you should forget about everything and surrender yourself to another sins. Walk one step at a time. If you aren't able to get rid of a sin right now, just be careful to not add more sins to your daily life. If you are able to maintain just one it's progress already, although it can still get better, until you completely eliminate all of them.
That is what the preacher meant. You may be a gambler and even though it's against your religion, it doesn't mean you should stop praying and praising God. God knows our failures and imperfections, but He still love us and believe in our potential of becoming better human beings.
But that also does not mean that you start believing that this one sin (in this case gambling) is right to do and you find yourself in such a situation where your heart and mind feel satisfied that since you are doing many other good deeds, this one sin can be done and there will be no questioning about it.
This message can taken in both directions if you do one sin, then it should not stop you from doing other good things but at the same time if you are doing many good things. you should not use it as an excuse to commit a few sins, knowing that these are not allowed in your religion.
well, how you will live your life depends on what you truly believe in life. you may have your religion as your guide and assist what would you classify as a sin or not, but it is still up to you how you will apply it in your everyday life.
so committing one sin doesn't mean you are not a follower of your religion. as a human, you are prone to committing mistakes. and you can make amends with such mistakes or sin as you called it, by following some rituals that you think can salvage you depending on your beliefs. just accept the fact that no human is perfect to live on this planet. and it is up to you how you interpret things and live a meaningful life.