a sad quote

@NicoRose Apologies...But by a love that is not meant to be ...did you mean it's a secret love, a love forbidden by society, a love doomed by fate or one that arrived unexpectedly but was never meant to stay? (It is to narrow it down)
Tagging some poets who may be able to help you , If I may ... @ZenArashi @BastionKnight @suu1309 @twerp

@NicoRose

*Thanks @azurePond shyly for the tag*

I was not sure if you what you meant by suggestions was tips, inspiration, or thematic hooks, so I hope my modest contribution to this post is useful in some small way:

Try and get inside the character(s) mind and imagine what they feel. Or if you can draw on your own experiences, use those. You need not make it sound dramatic, as honest and heartfelt emotions will be much more impactful. 

Use imagery which is vivid. Nature works well for its beauty, fragility, and transient nature. Celestial or elemental forces give a sense of passion (either positive or painful). Colours and sensations can add depth to emotional descriptions or even work as replacements for an emotion word. Similes are useful for subtle suggestions of intensity of emotion; an example that comes to mind is from Romeo and Juliet:

"My bounty is as boundless as the sea,
My love as deep; the more I give to thee,
The more I have, for both are infinite" - William Shakespeare

When using metaphors, classic choices can give the poem a gentle, naïve quality. But for more vibrant emotional pieces I would suggest that you try more unusual pairings. John Donnes 'The Flea' is a good example of an unusual extended metaphor for a love/lover that can elevate standard love tropes into something memorable. In it the poet uses a flea as a symbol of their illicit love, of commitment to each, of physical love, and of the vagaries and passions of his and his paramours relationship. The more unique the metaphor, the more it will likely make the poem stand out.

As you have said the love is not meant to be, playing with contrasts can give the sense of being torn and add to the atmosphere of desire versus reality. Light vs dark, warmth vs cold, passion vs restraint, joy vs despair, desire vs destiny, etc.

The particular choice of structure can add a great deal to the emotional feel of the poem: Haiku can give it a subtle, immaculate perfection or capture a fleeting moment. Free verse can make the poem feel raw and unfiltered, as if one is spilling out everything in honest declaration. A single rhyming couplet can give a powerful and memorable impression that capture the intensity of the feelings. A longer stanza can allow emotions to be built up and reach crescendo or maybe drawn down into softer regret and/or resignation. Maybe also consider the rhythm and sound of your lines; soft consonants or vowels sounds and unstressed words can give a gentle feel, whilst harsh and stressed ones can give a more intense and immediate feel and highlight pain or fierce emotions. Steady and repeating rhythm and symmetrical syllable counts can make the poem feel hypnotic/melodic and work nicely for conveying an air of appreciation/adoration or make the poem feel intimate. Conversely, irregular choices can convey scattered thoughts, emotional turmoil. A single offbeat line or couplet in an otherwise regular stanza/poem can bring sharp focus on it...a bit like suddenly cutting a piece of music short with an off note or loud clash, giving it great impact. 

Spend some time thinking about the last line. It will sum up the feelings you wish to convey and leave the lasting impression of the whole poem, so it should do justice to what you are trying to create.

Hmm, that is all I could think of at the moment. I freely admit that my knowledge and skillset is very limited, but hope that something I wrote might prove useful. Apologies if it was a bit long winded.

Good luck, and hope you choose to display your poem and art once it is complete.