how do 당신 know for sure that your a bronie?

When 당신 watch and like the show and 당신 are an active part in the community.

It's not really whether 또는 not 당신 know you're a brony. It's whether 또는 not 당신 believe you're a brony.

당신 can like the show without being a brony. 당신 don't have to call yourself a brony simply just because 당신 like the show 또는 interact with the brony community.

Look up Joshscorcher (A.K.A. The fiery Joker) on youtube. He has done MLP episode reviews, and he has actually said he likes some episodes (for instance, he said he "loved" the royal wedding episode). He has even interacted with the community in some ways, like going to Bronycon.
However, he has actively stated time and time again that he doesn't consider himself a Brony.

So to answer your question: I believe 당신 just have to like the show and actively consider yourself a brony. There's no "knowing" involved. 당신 simply have to "believe" 당신 are one.

Essentially what btflash said. Being a brony is a choice, not a status/rank. If 당신 don't consider yourself a brony, then 당신 aren't. The donning of an internet surname isn't mandatory to do anything that they do.

Brony is a pretty basic thing: It says "I like My Little 조랑말 Friendship is Magic" in one word. The connotation of that could be "MLP fanatic", but nonetheless, it's still just an optional title. People shouldn't look 더 많이 into it than that. It's built up a stigma and brings about idiotic generalizations about the fandom, so some 팬 choose not to use the word "brony" to describe themselves.

The gist is that if 당신 think you're a brony, cool, if not, then it's the same matter; 당신 can't be treated differently just because 당신 choose not to use the surname. It's all the same to me.

When 당신 doze off frequently thinking of ponies. :D

When you're obsessed with MLP:FIM.

I'm not a Brony though.... :/

I'M A PEGASISTER!!! :D

당신 have watched too many MLP FiM.

Like the others said being a brony 또는 a pegasister is a self dubbed 제목 but I believe that there are levels of broniness
(each lvl includes the 이전 ones)
Lvl 1 u consider yourself a brony and u watch mlp fim
Lvl 2 u r an active community member and know all the mane sixes names, element and traits
Lvl 3 u know about the cmc, zecora, spike, silver spoon, diamond tiara, big Mac, cherrilee, granny smith and some jokes like 20% and draw only ponies
Lvl 4 u know the famous background ponies lIke derpy, Bon Bon, Lyra, and Octavia and can quote some of your fav episodes
Lvl5 u know all the background ponies and can recite the plot lines of your fav episodes, quote all the episodes, know some songs 의해 heart
Lvl 6 u know the plot lines of all the episodes and know most songs 의해 heart
Lvl 7 u know all the songs and the famous fanfics like 컵케익 and write your own