That is very true. Buying only what is needed is a great discipline to have when stretching your dollars. It's amazing how many unnecessary "nice-to-haves" we can accumulate over time!
I second the notion of assessing the necessity of purchases. I've found that sleeping on impulse buys overnight helps me gauge whether I really need an item. This physical separation from the item, combined with a strict 24-hour rule, often cools my desire for it and saves me money.
Your tip on negotiating prices is also spot on. Many people may not realise it, but most prices are often open for negotiation, especially if you're a long-term customer or purchasing in bulk. It pays to be assertive and ask for a better deal.
These strategies, though simple, can certainly help make a difference in financial management.