I find with DS-almost-2.5, dubbed "the tornado", we have to explain in great detail before an incident happens why something isn't a good idea. Prophylactic discipline.

Now, I try to hold/hug DS when he's oppositional or being disciplined. I find the gentle physical contact conveys a very strong "I care about you" message and contextualizes disciplinary wording. We keep the emphasis on the behaviour, not the person, and praise randomly when DS is behaving well.

I agree with Dude that consistency is the best gift you can give your child. Set only essential, hard boundaries and be laser focused about enforcing them. I pick one or two behaviours to work on and aim for 90%+ consistency in making corrections. It usually takes a week or two to remediate a behaviour this way and, because DS hears the same message constantly, he is able to quickly assimilate the expectations for him.

What is to give light must endure burning.