One of the best pieces of advice I can give a parent regarding ANYTHING they try to implement with their child is that consistency is key.
Many times parents ask why a specific strategy isn't working. They tried it for a few days and it doesn't seem to be working; behavior doesn't seem to be getting better.
In these situations, my advice is always the same: consistency is key. You have to keep trying and keep working at it. Change doesn't happen over night.
In fact, with the new strategy that you're using, you are actually teaching your child a new skill, a new system, or a new way of doing things. It takes time for your child to learn that new skill, new system, or new way of doing things. Along with time, it takes consistency.
Maybe you're using a timer for the first time. Maybe you're using first-then statements. Or you could be outlining expectations for the first time. Maybe you are no longer giving in to your child's whining when he wants that piece of candy. Incorporating a routine into your schedules day is another great example. All of these take time. All of these things take consistency.
When you feel like giving up, when you feel like nothing is working, when it seems like behavior isn't getting better, continue to implement whatever strategy you were advised to use (unless you have a good reason not to continue or you were told by a professional not to continue). Ultimately, our children are learning a new way of doing things, and this learning takes time.
If you want to know one of my biggest and best pieces of advice, it's this: consistency is the key to your parenting success.
It may take time. It may take work. In the long run, you'll be glad that you were consistent with your child and you pushed through the rough patches... the grass is greener on the other side.