The software will tell you your RoR. One way to do this is to bet a fraction of Kelly. This reduces your RoR exponentially while only reducing your win rate linearly.
I'm hoping you mean to recalculate after every session loss. Surely no one recalculates after every bet lost. If you have a reasonable bankroll, the difference in one bet from the next at the same true count would be negligible. Second, when you do have a significant loss, you really should use the software to recalculate your reduced spread. This what most people would actually do. If you do this, then your RoR will be reduced but will not be zero. I say this because, when RoR gets you, it gets you quickly, meaning that when you bet full Kelly for a session, the risk of losing it all during that session is very real.