It is always difficult to live frugally when all around you seem to have more possessions, more money and simply more fun. There are few people in the world who do not enjoy having new, enjoyable possessions which can make life easier, more varied and overall just more fun. The risk of seeing life in this way is that it can make people go to extreme lengths to keep up. No small amount of the financial turmoil that is seen on an individual basis very frequently happens for this very reason. When people around you always seem to have the best clothes and gadgets, and be enjoying life more, there is a real chance that they are living beyond their real means.
Spending money is fine, as long as there is money there to spend. Otherwise, it needs to be considered long and hard in the context of your situation. If you are making a purchase on a credit card, ask yourself if you can afford to make the payment that is required at the end of the month (or whenever your payment cycle places the due date). If it is a matter of making the purchase now and worrying about how you will pay for it later, it is really a good idea to refrain.
Think of it like this: credit cards make it easier to spend money, but that money is not technically yours. Spending money that you need to pay back, and not having the means to pay it back, is like trying to outrun a hungry lion. The credit card may act as a vehicle to escape the lion, but sooner or later you run out of fuel.