Never fill a box until it is so heavy that you can't lift it safely.
1	Never	never	ADV	RB	Polarity=Neg	2	advmod	2:advmod	Discourse=explanation-motivation:22->25:1
2	fill	fill	VERB	VB	Mood=Imp|Person=2|VerbForm=Fin	0	root	0:root	_
3	a	a	DET	DT	Definite=Ind|PronType=Art	4	det	4:det	Entity=(23-object-new-cf1-2-coref
4	box	box	NOUN	NN	Number=Sing	2	obj	2:obj	Entity=23)
5	until	until	SCONJ	IN	_	9	mark	9:mark	Discourse=mode-manner:23->22:0
6	it	it	PRON	PRP	Case=Nom|Gender=Neut|Number=Sing|Person=3|PronType=Prs	9	nsubj	9:nsubj	Entity=(23-object-giv:act-cf1-1-ana)
7	is	be	AUX	VBZ	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	9	cop	9:cop	_
8	so	so	ADV	RB	_	9	advmod	9:advmod	_
9	heavy	heavy	ADJ	JJ	Degree=Pos	2	advcl	2:advcl:until	_
10	that	that	SCONJ	IN	_	14	mark	14:mark	Discourse=mode-manner:24->23:0
11	you	you	PRON	PRP	Case=Nom|Number=Sing|Person=2|PronType=Prs	14	nsubj	14:nsubj	Entity=(2-person-giv:inact-cf2-1-ana)
12-13	can't	_	_	_	_	_	_	_	_
12	ca	can	AUX	MD	VerbForm=Fin	14	aux	14:aux	_
13	n't	not	PART	RB	Polarity=Neg	14	advmod	14:advmod	_
14	lift	lift	VERB	VB	VerbForm=Inf	9	advcl	9:advcl:that	_
15	it	it	PRON	PRP	Case=Acc|Gender=Neut|Number=Sing|Person=3|PronType=Prs	14	obj	14:obj	Entity=(23-object-giv:act-cf1-1-ana)
16	safely	safely	ADV	RB	Degree=Pos	14	advmod	14:advmod	SpaceAfter=No
17	.	.	PUNCT	.	_	2	punct	2:punct	_
