1 In Judges 6:13 Gideon used he excuse of his circumstances.
"And Gideon said unto him, Oh my Lord, if the LORD be with us, why then is all this befallen us? and where be all his miracles which our fathers told us of, saying, Did not the LORD bring us up from Egypt? but now the LORD hath forsaken us, and delivered us into the hands of the Midianites."
2 In Judges 6:15 Gideon used the excuse of his status. He didn't think he was worthy.
"And he said unto him, Oh my Lord, wherewith shall I save Israel? behold, my family is poor in Manasseh, and I am the least in my father's house."
The grace of God makes us worthy to be used by Him (1 Cor 15:10). It's a privilege to be used by God. We need not focus on our circumstances or inabilities but his grace that qualifies us.