What is the number 1 thing that all of us want? You my have a number of answers, but ultimately it will lead us to happiness. What ever we do, we do it for happiness. As long as it makes us happy, I don't think you should stop your self. If impulsive buying makes me happy, why shouldn't I do impulsive buying? 

I cannot minimize my expenses because I need to continue spending on things that I am spending. You might say stop eating junk foods to save money. As long as eating junk food is giving me happiness and I am not overdoing, why should I stop buying junk food and constrict myself from happiness.