This might sound like a silly question, since he's ta'veren, but read on!
As early as book 1 of WoT (at least by the time they meet Loial), we know that Rand, Mat, and Perrin are all ta'veren. I assume this is something you're born into, so they must always have been ta'veren. This shows itself in various ways over the course of the books in coincidences and unlikely events happening close to them. By far the most obvious manifestation of Mat's ta'verenianity is his incredible luck,
which allows him to win almost every time at dice and cards and which, along with his memories from past war leaders, brings him such vast success in battle that by the time of book 6 he's gathered his own army.
But this only manifests itself in the middle of book 3, when Mat moves from tavern to tavern in Tar Valon:
He had always won more than he lost, as far as he could remember, and there had been times with Hurin, and in Shienar, when six or eight tosses in a row won for him. Tonight, every toss won. Every toss.
And later on the same page (p.343):
He knew he was lucky. He could always remember being lucky. But somehow, his memories from Emond's Field did not show him as lucky as he had been since leaving. Certainly he had gotten away with a great deal, but he could remember also being caught in pranks he had been sure would succeed. [examples] But it was not just since leaving the Two Rivers that he had become lucky. The luck had come once he took the dagger from Shadar Logoth.
So what's going on here? Is it just to do with being ta'veren? Is there really a Shadar Logoth connection, and if so why does it stay even at this point, after
his bond with the dagger is broken?
He always remembers that one night in Tar Valon as being the time when his luck was at its height. Since then he's won most of the time but not every single time. So what was special about that one night? Was someone channeling using that dice ter'angreal that Nynaeve, Elayne, and Egwene talked about in the same book?
So here are some theories for why Mat's lucky:
- ta'veren (but why does it kick in so late?)
- dagger (but why does it stay on?)
- ter'angreal (ditto, unless someone's planted it in his dice cup - now that's an intriguing theory!)
Thanks in advance for any suggestions!