Have a positive mindset is similar to being in a good mood. In gambling, being in a good mood is important for both analysis and bankroll management to avoid missing bad emotion into the business. Positive mindset in gambling works like magic just like positive affirmation does in trading and meditation in life generally. Finally, having positive mindset also makes one believe and trust his selection and strategy which is necessary for longevity in gambling.
Let us put it this way - you will only have good mood and carefree gambling experience if you are playing with extra funds and you are not worried about losing it. That is, it is not your borrowed money and simply your spare funds to enjoy. Otherwise, I don't think you will enjoy playing while you are thinking of recovering it because you need to pay somebody afterwards.