What arguments does Friar Laurence use to convince Romeo that his despair is not justified?

In Act III, Scene iii, Romeo is in despair after the Friar reveals he has been banished for his role in the deaths of Mercutio and Tybalt. His despair revolves around the fact he will not be able to see Juliet because he will have to leave Verona. At one point he throws himself on the ground crying. The Friar uses four arguments to assuage the distraught Romeo. First, in his long monologue he tells Romeo he should be grateful that both he and Juliet are still alive. He argues that Tybalt could have killed him. He says,

Thy Juliet is alive,
For whose dear sake thou wast but lately dead:
There art thou happy. Tybalt would kill thee,
But thou slewest Tybalt: there art thou happy

Second, the Friar believes the Prince was quite lenient in sentencing Romeo to banishment. The Prince could have opted for death as he had declared earlier in the play that future fights in the street would be punished with death. Friar Lawrence says,

The law that threatened death becomes thy friend
And turns it to exile: there art thou happy.

Third, the Friar tells Romeo that he can still go to see Juliet for their honeymoon. They can be together one more night before he goes to Mantua.

Finally, the Friar assures Romeo that once things calm down in Verona, the Friar can announce the marriage, beg the Prince for a pardon, and then Romeo may return to Verona to be reunited with Juliet. He says,

But look thou stay not till the watch be set,
For then thou canst not pass to Mantua,
Where thou shalt live till we can find a time
To blaze your marriage, reconcile your friends,
Beg pardon of the Prince, and call thee back
With twenty hundred thousand times more joy
Than thou went’st forth in lamentation.

Romeo is mollified for a time as he tells Juliet he has no doubt they will meet again in Act III, Scene v. Unfortunately, they never come together again as Romeo kills himself in Capulet's tomb before Juliet awakens.