It is probably the most common advice most finance websites and blogs offer. It is easy to type, but much harder to do in real life, expecially when you have established a comfort level that you are now as used to. To simply stop living that way is a near impossibility.
In order to this personally, I took a different approach to it. Instead of changing my current life, I decided to baseline my lifestyle at that particular moment in time. I decided that from that moment on, except for emergencies, anything that I buy would not increase my monthly expenditures. This was suprisingly easy to do.
Instead of putting out another $20 per month for a gym membership, I would reduce another cost to accomidate it. For instance, dining out. If I wanted digital cable, I would change my own oil.
Doing this for every added expense that you become committed to, in addition to normal raises, tax refunds, etc. makes the reality of living within your means happen automatically.
I used to think, along with many of my friends and family, the way to success is to increase income to afford the things you want. Trust me it is much easier to find money in your current budget than it is to earn more.
Living within your means does not mean increase your means, it means to decrease your living.