Definitely one of the hardest achievements around, but if you decide to keep playing Hexic to become good, this should come around in time.
Remember, the game is NOT about matching groups of hexes together. It's about creating starflowers, then pearls. That should be your mindset. Every move should work toward creating a starflower, maneuvering stars together to create a pearl, grouping pearls, or defusing a bomb. Everything else is a bad move.
Things to keep in mind:
1) Defusing bombs is always the top priority. Always.
2) You should always have lots of stars on the board. They allow a lot better maneuvering and piece movement. In fact, until it's hard to move without comboing stars, keep making them. Make the pearl when you pretty much have to do it to clear out some of the stars.
3) The best place to make a starflower is centered on a star. It's easier to move pieces into place, you get more points, and the new star is dropped from up above, where it's less likely to result in comboing stars.
4) Think through your moves before making them. It's not a timed game - make sure you're not going to accidentally make a combo before moving. Accidental combos are the quickest ways to wipe out clusters of stars.
5) Be extremely careful when going for the pearl flower. Use a star as the center, and double and triple check each move once the pearls are nearby. Nothing worse than accidentally comboing three of them when you're close. Don't even move the pearls close together until you have all six to prevent a runaway cascade from comboing them on you.