Southern leaders believed that their way of life which included the institution of slavery was in danger from the free States of the United States. Their solution was to become an independent nation and avoid further conflicts over slavery with the Northern States.
Independence.
To maintain its independence - and retain the cotton revenues.
The focus of the Civil War was, originally, for the South, or the Confederates, to gain independence from the Union. Later in the war, the focus became to free the slaves in the South. This was caused by the Emancipation Proclamation.
2 fight 4 independence
The main elements for the South in the US Civil War ended in a disaster. After four years of waging war to gain its independence, the South lost over 300,000 men and huge losses in property that the war destroyed.
During the US Civil War, and in fact before the war, the South's government was the Confederate States of America. This "new" nation wanted and fought for its independence from the US ( Union ).
Independence, autonomy, self-determination, and the right to own slaves.
They are NOT the same. However Civil war may pave way for Independence like Bangladesh. And civil war may not lead to independence at all. After Independence civil war may happen like US of America, which did not result in another spell of Independence. The American War of Independence in 1775 was a civil war. The colonists were British just as much as the British in Barbados or the Isle of Wight. The only became "Americans" after they had gained their independence and been recognised as a new country.
The Confederacy wanted and believed it could achieve independence from the US. It almost happened.
South Sudan gained independence from Sudan in 2011 after a long civil war.
The single most consistent advantage for the South during the US Civil War was that they only needed a successful defensive war to win independence.
The South fought a War of Attrition to make the Northern population sick of war, and make Lincoln negotiate peace.