This is an interesting statement to consider in relation to this famous Scottish poem. Which other emotions do you think are not increased when they are expressed? In some ways, I think that expressing an emotion automatically helps to increase that emotion, as you think about it and give voice to it in a way that means your feelings are going to be heightened. Certainly I think we can argue that this is the case in this poem, as the thought of the speaker's beloved is something that only serves to heighten his delight in her. Consider the second verse of this poem:
As fair art thou, my bonie lass,
So deep in luve am I,
And I will luve thee still, my Dear,
Till a' the seas gang dry.
The thought of the beloved's "fairness" leads the speaker to declare that he will love her constantly and faithfully "Till a' the seas gang dry." His delight and love for his beloved is evident throughout the poem, and seems to be reinforced through the voicing of his love for his beloved, therefore proving your statement.