Secession may be a few "militia men's" wet dream but it isn't happening
There is no capability under the Constitution for any individual state to unilaterally secede from the Union, settled law under Texas V White 1868
http://supct.law.cornell.edu/supct/html/historics/USSC_CR_0074_0700_ZO.html
Cuts both ways, there is no way for a state to be excluded from the Union.
In
THEORY a mutual agreement could be agreed between both the individual state and the rest but to even do that at the very least a constitutional amendment would have to raised and passed then it would have to stand scrutiny in the SC etc etc.
So, State X says they don't want to play and want to keep their ball
State X Constitution would have to be amended
State X would have to petition Congress
State X has to convince two-thirds of both houses of Congress to vote to propose an amendment, or
State X has to get two-thirds of the state legislatures ask Congress to call a national convention to propose amendments. (This method has never been used.)
Assuming the petition works then they have to ratify the amendment
Three-fourths of the state legislatures approve it, or
Ratifying conventions in three-fourths of the states approve it. This method has been used only once -- to ratify the 21st Amendment -- repealing Prohibition.
Sorry to pop some peoples bubbles with reality