In my opinion, someone gambling for fun understands and accepts that they are likely to lose the money they wager. The money spent is viewed as the price of admission for the entertainment experience, not an investment or a serious attempt to get rich. Losses are seen as part of the game, not a catastrophic event. 
Yes, that is the definition of responsible gambling where a gambler is able to accept whatever the results are at the end of the game, especially defeat, simply when they win they feel happy and when they lose it does not affect their mental and psychological, on the other hand what you describe is true that responsible gambling and also for fun is when a gambler considers that the money they spend is a tool that they will exchange for entertainment and pleasure, meaning from that alone we can conclude that they are ready to lose because what they are looking for is pleasure and not chasing victory and also because they know that gambling is not a place to get rich, another thing I just hope that all gamblers can have that mentality and mindset.