Scents can be big triggers for people.
Just like you remember your father or grandfather for the smell of Old Spice.

You also will find that you can set triggers by using the same scents over and over again when a certain thing happens.
Example: would be having your partner wear the same scent during lovemaking. After awhile your sex drive will rise when you smell that scent.

You can also find triggers with sound or by touch. Such as feeding dogs and ringing a bell or your partner stroking your hair or arm a certain way becomes a trigger for your most wanted attention.

and I don't mean stroking yourself off either