I think we all know what my answer is going to be and you’re not going to like it:
It’s the simplest answer to this,however is not as simple as that !…
Bad habits can be really difficult to get rid of for so many reasons . Muscle memory kicks in and take often take over so a very hard physical and conscious effort needs to be made to change this .
In children it’s really important to try make sure they don’t form bad habits as they find it particularly difficult to get rid of ( and usually quit lessons because they then begin not to like them-such a sad and unnecessary reason to end tuition .). Adults have more mental ability to make a conscious effort at changing their behaviour . Children often form bad habits to make things easier for themselves and then when they need to change to a harder way of learning you often get people dropping out.
I find practicing over and over again until you can override the bad habit is the best way to beat it. This can sometimes take an age but I have found when I learn songs and then realise I’ve learnt it wrong I need to take a good 20 mins everyday to just focus on that section until my new muscle memory becomes the new norm . It takes a while and each person takes a different amount of time but if you have the desire to really change it then you will.