I heard once Rabbi Gottlieb say bshem the Hazon Ish
“Some people have 613 Mitzvot and some people have 613 challenges…”
@ AviK
Did you really use the GR”A as an example to make your point?! Please see the introductory to Chai Adam written by the Gaons son in law. Also see what his sons wrote in their intro to Shulchan Aruch.
As for the Rambam. You are aware that he was supported by his brother for years while he sat and learned Torah FULL TIME. This. Ended when his brother perished on a business trip and the Rambam lost this means of support. See the Rambams letter to Rabbenu Yonitan M’Lunil that secular studies where never regarded by him as more then handmaidens to the Torah.