I second you on this thought. The positive mindset is good, but it is only progressive if used in the right field or activities. Gambling is not the right place to have a positive mindset, it's better you use the gambling mindset in gambling, because with that, you will be prepared for the worst.
If you are using a positive mindset in gambling, you will only find yourself repeatedly gambling regardless of whether or not you are losing. This is just a motivation that can put you in trouble of persistent hope that may never be fruitful.
This doesn't necessarily mean that you will continue playing regardless of whether you're winning or losing. If you set a budget limit for yourself, you will simply stop, and a positive attitude will just help you cope more easily with a loss if you've had a bad day. So, positive thinking has a good effect on all areas of our life, but how much we lose depends on the limits we set and on our discipline, which can keep us from continuing to play further.
Overall, to keep yourself away from big losses in gambling, it is very important to limit yourself to a certain amount of budget according to your ability, you have to be responsible towards gambling, you will naturally lose in gambling, but even at that time you have to control yourself with responsible behavior and accept that loss and get out of gambling. Regardless, the most important thing is to stop yourself, when you can stop yourself at the right time in gambling, only then you can really win.