Sam M's poem is a list of things the person it's addressed to will never see, hear or know. The speaker loves this person, hides it, and has been hurt by them. One line says they were badly hurt "that month," and another calls the person "a player," so the speaker seems to think they aren't serious or faithful. The poem also hints that it's one of several the speaker has written, since the opening line talks about "these" that the person will never see.
The feeling shifts as it goes. At first it sounds like sadness: love that stays hidden, tears no one witnesses, a voice that gives away more than the speaker wants. Then the repeated "You'll never" starts to sound more like self-protection. The last line, "And for that I'm grateful," turns the whole thing around. Staying hidden feels safer than being exposed. The mood is bittersweet and guarded, a private confession made by someone who would rather feel the ache alone than risk being rejected.