You might give in every now and then to impulse buying, and that's okay. Impulse buying becomes a bad habit when you are constantly broke from your spending habits and/or what you've bought goes to waste. Let's say you're an impulse buyer when you see a bargain. Your house is so full of $1 trinkets and $5 junk that you have no storage space and the place always looks messy. Remember, just because it's on sale, doesn't mean you actually need it.
If you've given into impulse buying, there is a way you can make up for it. Sell something that you never use. Make sure the item you're selling can be sold for an amount close to what your impulse buy cost. So if you bought a $10 sweater on impulse, sell that pair of $30 shoes you never wear. If you can get more than $10 for the shoes that's great, but if not, at least try to sell them for an amount close to what the impulse buy costs.
We all give in to our temptations every now and then. What's important is that you recognize the problem and are learning how you can control it.