Tamil Eelam is the name Tamil separatists give to the country they want to create on the island of Sri Lanka. The history of Tamil Eelam is an interesting example of just how badly wrong things can go for secessionist regimes. For many years, the Liberation Tigers of Tamil Eelam (better known as the Tamil Tigers) were able to successfully defend the territory of notional Tamil Eelam from the Sri Lankan army. They established a de facto regime, essentially a garrison state, in the liberated territory, but were unable to get any external recognition of their independence. More recently, the Sri Lankan military was able to exploit internal divisions within the Tigers. In a series of bloody offensives, the separatist zones were over-run. The Tamil Tigers' last enclave was eliminated earlier this year, with massive loss of life, including that of the Tigers' leader.
I do not know if any general lessons can be learned from Tamil Eelam's Gotterdammerung, but it does illustrate the precarious situation in which unrecognised countries find themselves.