With a placid disposition, rising above fear, established in celibacy, with mind restrained, devoted to Me (the Guru), let him strive for yoga regarding Me as the Supreme.
The whole exercise is mental. Mind and intelligence should not run helter-skelter. They must be restful. Unrestricted indulgence in the world is what causes fear. This kind of inner striving frees one from all such fear.
Krishna specifically speaks of celibacy here. Sitting alone in seclusion should not bring in any un-celibate thought or indulgence, for which there is all possibility. Here too viveka, discrimination, is the only safeguard.
All thoughts and emotional urges arise from the mind. By watchfulness and resolve, all deflections should be dispensed with. The only thought, reliance, refuge and anchor must be the Guru, who alone fosters the best thoughts of welfare for the disciple, which even idols and other depictions will not be able to.
Regarding the Teacher as the supreme goal, strive. This is the exclusive pursuit of yoga.