すぐに寝たほうがいい。

immediately; at once; directly; soon; before long; shortly; easily; without difficulty; right (near); nearby; just (handy)

at (place, time); in; on; during; to (direction, state); toward; into; for (purpose); because of (reason); for; with; by; from; as (i.e. in the role of); per; in; for; a (e.g. "once a month"); and; in addition to; if; although

to lie down; to go to bed; to lie in bed; to sleep (lying down); to sleep (with someone, i.e. have intercourse); to lie idle

point (of a sword, etc.); pointed verbal attack

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

good; excellent; fine; nice; pleasant; agreeable; sufficient (can be used to turn down an offer); ready; prepared; profitable (e.g. deal, business offer, etc.); beneficial; OK