Let's take another look at this reaction. In a reaction one molecule with a specific structure is changed into another molecule with a different structure. Since structure depends on bonds, bonds must be broken and made in a reaction. We can tell what must have happened by comparing structures. If we look at an acid-base reaction, we can see some features that may help us.
Acids are compounds that give up hydrogens to bases.
Let's look at the bonding changes involved. Electrons which bonded the proton to the atom it started with stay with that atom. Notice that we can symbolize this by using curved arrows to show the flow of electrons as bonds are broken and made. It must be in the other reactant, but there doesn't seem to be an unshared pair there. Let's try that as a base and use our curved arrows to keep track of the electrons.