Sonnet 43 uses both repetition and variety to intensify meaning.
There are several lines that begin "I love thee..." While these lines begin in the same way (repetition), the rest of the line varies.
For example, I love thee freely...I love the purely...etc. In these lines, EBB is able to discuss the many dimensions of her deep love. Her love has many sides to it, as the repetition and variety explain.
The use of blank verse enjambment intensifies the contemplative ad meditative of the poem. Blank verse allows for freedom of form enhancing the tone of the poem which shifts from being hopeful to being hopeless
the use of enjambment helps hold the readers interest across line: to him in the love of nature holds communion with her visible forms she speaks a various language for her gayer hours
