Yes. I also estimated my losses after i got home from a casino, especially if i lose a lot of money, so that i could if i gamble too much. It is also the reason why i only bring the only money that i need in gambling, so that it would not be a problem if i lose a lot of money and i already know how much money will i only lose.
Yes it is okay to calcuate the amount amount of money you are using when gambling, especially if you are begineer gambler, for you to know how to manage your money and allocate it in different ways. In online casino it is okay to put even 1btc if you have but only bet little by little amount, do not put large amount at first bet because you might lose it.