The crisis in Greece affect the euro very much. If the problem is not solved in near time or if Greece doesn't leave the European Union than the euro will drop. That is the reason why the union has to do something about this 
the european union will do everything to keep greece inside. if that means giving them more billions that they will never get back, then they will still do it. if greece leave the euro and it turns out to be great for them, then other countries may decide to leave as well. stakes are way too high.
The reasons for Greece to leave are far more better for Euro than them to stay. Greece will no more be a financial liability, A Greek exit demonstrates that the entire Eurozone will not be held hostage be a trivial small irresponsible partner. It will also set an example for other countries, Perceive the situation as Greece being a bad kid who got kicked out for being a bad boy. The only reason Greece has been a failure is because of incompetent Greek public governance.