I fucked up the #1 rule

I have 5 years of mma experience and i am well rounded in grappling and striking, im a pretty big guy too. There was this boxer i had beef with for the past couple of weeks and I asked him to fight me (this was before i knew he had experience in fighting). He was a bit smaller than me and it didnt look like he was anything special. Anyways, we fought at this big field where no one would see us, it was just my friends and his friends with us.

When he came, i saw him with boxing gloves and i obv assumed he was a boxer and i was just going to leg kick tf out of him.

No, i was wrong. He used his footwork to get in and out of range so I then started throwing teeps at him but he came back out and came back in and start punching me. I THOUGHt i could strike with a boxer because they cant defend kicks but he kind of did with his forearms and evaded it with his fucking footwork. Then the worst part is, when i tried to go for a takedown he pivoted out the way somehow, honestly im not sure what he did but he got out the way and just jabbed me after, The dude was playing with me the whole time.

So now i feel useless, all my training was for nothing. I got beaten by a boxer out of all peoplle. No offenec to them

I underestimated my opponent