Here is the heart of Krishna's practical argument, distilled into two crystal-clear outcomes. If you are slain in battle, you attain heaven. If you win, you rule the earth. Either way, there is no losing. So arise, O son of Kunti, and fight with firm resolve.
There is a clarity here that cuts through every doubt. When both roads lead somewhere good, hesitation has no logical footing. It is like a farmer who discovers that whether it rains or stays dry, his particular crop will thrive. What reason remains to sit idle and watch the sky?
The word 'kritanishchayah' — with firm resolve — is the key. Krishna does not want Arjuna to stumble into battle half-heartedly, still torn and confused. He wants a clear decision, a full commitment. Action born of clarity is different in quality from action born of compulsion.