Agree with pp who say the love, trust, respect and communication have to be there before adolescence strikes as ultimately it is the quality of your relationship that will stop them going seriously off the rails.
Other than that, change your style of parenting from top down to side ring supporter. Step back and give them responsibility for their own decisions as much as possible, rely on natural consequences for the rest, and only step in if their personal safety or mh is endangered, and adopt a two-pronged position of belief in them and curiosity about how they will handle a certain situation. For everything else, pick your battles and don’t take everything they say or do personally. Ninety per cent of the time the angst is about them, not you.
Also example, example, example. Be a good role model. Live a fulfilling life! Walk the walk don’t just talk the talk. Teens are very aware of what we do, rather than what we say. So if you want them to grow up hard-working, loving, respectful, curious about the world, brave, resilient etc then it very much helps if you imbue those qualities too … and most of us are far from perfect … but the important thing is they see us genuinely trying and failing and trying again. And we need to show that growing up to be an adult isn’t all stress and problems and can be fun!
In other words, so much of parenting teens is focused on what we don’t want them to be doing but imho equally important is demonstrating how to live a balanced, meaningful and happy life, as that’s not an easy thing to achieve,
The other thing op, as someone who used to question my parenting at all times, is to chill a bit, your teens need you to be calm and positive in a realistic way.
The fact that you are questioning yourself continually op probably means that you are already a thoughtful and sensitive parent which means you probably are doing a great job. So relax! I never believed people when they said that a mother needs to be happy to be a good parent but honestly I think this applies to teens very much indeed.
So do everything you can to support your own anxiety, mood, mh etc and that in turn will help your dc. Dont continually question yourself to the extent that you are always anxious and you drive your mh in to the ground. If your teens are stressing you out, seek support for yourself first and foremost, as teens are like laser missiles when it comes to sniffing out our weaknesses 😄. And they need is to be a steadying hand while they negotiate the ups and downs, good
luck!
PS One last thing, when they get a bit chippy or know-it-all or frustrated, it means they need some more challenges in their life, and something do which is slightly above their current capabilities! 😉