I take gambling a bit differently than most people.
Instead of thinking of gambling as a source of income or a get rich quick scheme, both things which it is not, I think of it as purely for entertainment.
There is no responsible way to take gambling if not following your insight. My approach to gambling is the same as yours, i have never considered gambling to be a source of income for me, i also don't place expenses on any future winning from gambling, my income should cover that aspect.
In fact, if a gambler accumulates the total of what he thinks he can afford to lose he would know that he is losing what he cannot afford to lose. I think that any penny spent on gambling is a money the gambler have decided to sacrifice with the hope of getting a bigger amount and not because he can afford to lose it.
What's your position on this thought?
Aside gambling, think about other expenses you make only for you to catch the fun and entertainment. If you don't see gambling as fun that is when you come up with entitlement of making profits from gambling. I don't gamble using that initiative, if you do it is time to quit and see gambling only for the fun, whatever you make from gambling are just extra.