The structure of a sentence comes from the parts of a sentence, and a sentence can have many parts.
For example, every sentence--such as, "I love you"--has a main noun ("I") and a main verb ("love"). The sentence, "I love you," has another noun, called a "direct object": this noun is "you."
Sentences can also have adjectives and adverbs: In the sentence, "I love you dearly," "dearly" is an adverb, since it "modifies" (i.e., describes) the main verb "love."
A sentence can also have an appositive phrase, a noun phrase that modifies a noun by saying the noun in a different way. In the sentence, "I love you dearly, my sweetest one," "my sweetest one" is an appositive that modifies (says differently) "you." (And "sweetest" is an adjective modifying the noun "one.")
A sentence can also have a participle phrase, a group of words that begins with a participle, which is an -ing, -ed or -n verb. For example, "Having seen your good deeds, I love you dearly, sweetest one." The phrase, "Having seen your good deeds," is a participle phrase that begins with the participle (an -ing verb) "having."
Sentences also have clauses, which are groups of words with a noun and a verb. In the sentence, "Having seen your good deeds, I love you dearly, sweetest one, " the word group, "I love you dearly," is a clause, since it has a noun ("I") and a verb ("love"). But what if we add another clause? How about, "I am searching for a man of virtue"? In this clause, "I" is the noun and "am searching" is the verb (a present participle). If we put this clause in the sentence, we have to add a "subordinating" word to the beginning of it (for reasons that we shall ignore for now), so let's add "because." (There are dozens and dozens of subordinating words.) If we add this clause, we get the following sentence: "Having seen your good deeds, and because I am searching for a man of virtue, I love you dearly, sweetest one."
Some sentences have one or more prepositional phrases, noun phrases that begin with a preposition (e.g., on, to, for, of). The sentence we have been constructing already has two: "for a man" and "of virtue." But lets add another one. How about, "in the light"? If we add it, our sentence will look like this: "Having seen your good deeds, and because I am searching for a man of virtue, I love you dearly, sweetest one, in the light."
But "in the light" of what? In this case, we need another prepositional phrase, "of the morning," and we need to tack this phrase on to the end of "in the light," so that we get "in the light of the morning." Our sentence now looks like this: "Having seen your good deeds, and because I am searching for a man of virtue, I love you dearly, sweetest one, in the light of the morning."
But wouldn't the sentence sound better with another prepositional phrase that contrasts with the image of morning light? How about "in the darkness of the night"? If we add this prepositional phrase to the end of "in the light of the morning," we get this sentence: "Having seen your good deeds, and because I am searching for a man of virtue, I love you dearly, sweetest one, in the light of the morning, and in the darkness of the night."
This sentence can be made even larger and more complex, but let's stop here. If you learn all of the different parts of a sentence, you can begin to experiment with different sentence structures: some can be very logical, others very poetic (and a third group can be both logical and poetic). In my sessions with students, I try to teach them at least one new part of a sentence. Just as you need various objects to build a house (e.g., walls, roof, doors, chimney, windows, etc.), you need various sentence parts (or "grammatical units") to build a sentence. Hopefully, you've learned at least one new part from my Answer, and I encourage you to experiment in your writing by making sentences that have different parts in different places. It's fun!