If you do the job in a principled way, with diligence, energy and patience, if you keep yourself free of distractions, and keep the spirit inside you undamaged, as if you might have to give it back at any moment-
If you can embrace without fear or expectation-can find fulfilment in what you're doing now, as Nature intended, and in superhuman truthfulness every word, every utterance)- then your life will be happy.
No one can prevent that.
The body and its parts are a river, the soul a dream and mist, life is warfare and a journey far from home, lasting reputation in oblivion.
Then what can guide us?
Only philosophy.