Let’s pay attention to the meaning of the names. Normally, a name which alludes to removal of hatred should have preceded a name alluding to love. Leah seems to have reversed this sequence by proclaiming: "now my husband will love me" after the birth of her first-born, Reuben, whereas after the birth of Shimon she proclaimed: "G‑d heard that I am hated, therefore He has given me this one too." Another strange thing is Leah's conviction when Levi was born that "now my husband will grow attached to me." Was he not attached to her previously?

...she realized that he was not her true destined soulmate.

Righteous Leah had shed tears about her fate to become evil Esau's wife; this is why the Torah mentioned the softness of her eyes. When she now saw that she had become Jacob's wife, she realized that he was not her true destined soulmate. When she had a son she attributed this to an act of mercy by G‑d who had seen that she was not loved. The righteous always live according to the imperative of our Sages to always interpret everyone else's actions favorably. (Avot 1:6) It therefore did not occur to her that her husband could actually hate her.

People that think in that fashion are blessed. When Leah's first son was born she assumed that all she lacked was her husband's love. It was only when her second son was born that she realized retroactively that she had erred; not only had she not been loved but Jacob had actually hated her. When she said; "G‑d has heard," she meant that G‑d had been aware of something that she herself had not allowed herself to become aware of. When she had her third son she concluded that her previous reasoning that she was not Jacob's intended wife had been wrong too and that she was indeed Jacob's intended wife. She felt that the time had come when her husband would recognize this fact too and that his relationship with her would change for the better.

...truly matched pairs will remain together in the Hereafter.

Leah also was thinking of the time after she and Jacob would depart this world when she said "my husband will remain attached to me." She was now convinced that their souls would not become separated in the Hereafter as she was his true soul-mate. We have been told by the Zohar that truly matched pairs will remain together in the Hereafter. (Mishpatim section 102) She underlined the fact that she had borne Jacob three sons as the number three is indicative of something permanent, enduring.

She also foresaw through prophesy that Jacob would have four wives. Accordingly, she had fulfilled her destiny by bearing him three sons. When she subsequently bore Jacob a fourth son, she said: "this time I will thank the L-rd." She understood that up to now G‑d had treated her on the basis of justice, i.e. she had borne one fourth of Jacob's sons. Now that she had borne him four sons she thanked G‑d who had done more for her than she was required by justice.

[Selected with permission from the five-volume English edition of "Ohr HaChaim: the Torah Commentary of Rabbi Chaim Ben Attar" by Eliyahu Munk.]