What was abraham lincoln's reasoning when he refused to let the southern states secede?

For Lincoln, allowing American democracy to succeed was compatible with the ideal of freedom; allowing secessionists to destroy it (in response to a democratic election) was not.  In other words, Lincoln did not believe that true freedom was letting states do their own thing--and letting the pillars of American constitutional democracy run amok--but instead, in maintaining a union where the great experiment of democracy could flourish.  As Lincoln himself said quite clearly in the Gettysburg Address, he was  committed to making sure "...that government of the people, by the  people, for the people, shall not perish from the earth."  I suppose you can argue that Lincoln's vision of freedom was not worth the price, but you cannot deny that he had a vision of freedom--and that, for him, this vision was compatible with maintaining the historic, unprecedented political freedom that was achieved in 1776.

the captain of a steam ship naturally chooses the shortest route to his destination. since a sailing ship is usually pushed by winds and currents, its captain must find a route where the wind will probably blow in the right direction. tacking, i.e. using contrary wind to pull (sic) the sails, was always possible but wasted time because of the zigzagging required, and this would significantly delay long voyages. the early european explorers were not only looking for new lands. they also had to discover the pattern of winds and currents that would carry them where they wanted to go. during the age of sail winds and currents determined trade routes and therefore influenced european imperialism and modern political geography. for an outline to the main wind systems see global wind patterns.

pilotage or cabotage, in one sense, is the art of sailing along the coast using known landmarks. navigation, in one sense, is the art of sailing long distances out of sight of land.[1] although the polynesians were able to sail the pacific (with great difficulty) and people regularly sailed north and south across the mediterranean, before the time of columbus nearly all sailing was coastal pilotage

        it is some were in here? ///

an era of negotiation.

is that an answer to your question?