Did I play this right....or did I get greedy?

***** Hand History for Game 51574976655 *****
NL Hold'em 10 Buy-in + 1 Entry Fee Trny:12784292 Level:1 Blinds(10/15) - Sunday, April 24, 13:42:40 EDT 2005
Table Play money 3999450
Seat 3 is the button
Total number of players : 6
Seat 4: Biren ( $2430 )
Seat 3: KVillian ( $2560 )
Seat 2: wildcat007 ( $710 )
Seat 6: vern2333 ( $455 )
Seat 8: guizmo1 ( $1410 )
Seat 7: bdelkhunter ( $435 )
Trny:12784292 Level:1
Blinds(10/15)
** Dealing down cards **
Dealt to Biren

bdelkhunter calls [15].
guizmo1 calls [15].
wildcat007 calls [15].
KVillian folds.
Biren calls [5].
vern2333 checks.
** Dealing Flop **
:Td:
Biren bets [300].
vern2333 folds.
bdelkhunter folds.
guizmo1 calls [300].
wildcat007 folds.
** Dealing Turn **
:Th:
Biren bets [800].
guizmo1 is all-In [1095]
Biren calls [295].
** Dealing River **

Biren shows a pair of tens.
guizmo1 shows three of a kind, tens.
guizmo1 wins 2865 chips from the main pot with three of a kind, tens.

I knew he had two pair of trips and had me beat, but I got greedy and wanted to take down the pot, AND I was on a very nice draw.

Was that bad play? Or bad luck? Or both?

It was a bad play. You know he has you beat when he calls your semi-bluff on the flop. On the turn, when the board pairs, you could try to represent the ten, but it is likely that he has it. If you had the ten, would you immediately pump in a huge bet? Probably not. If he has one of the two tens, is he going to call any bet? Yes. You have 8 outs to win at showdown, or a 16% chance (5 to 1 against you). There is also a non-zero chance that your opponent had 2 pair, smooth called you, and just improved to a full house and you're drawing dead. I think your bet looks like a bluff, but might be hard to call with only say A8. So: if your opponent has two pair or better, he'll call and you're going to lose 5 in 6 times at showdown. If he has A8, he might fold to your bet, but he would also probably fold to another pot-sized bet. This bet does not get too many better hands than yours to fold (high 8s), and it gets called by hands against which you are drawing thin. If you bet another 300, you will probably get the same low hands to fold that your overbet gets to fold, and you will be called or reraised by the same hands that call your huge bluff. Your only risk with a more reasonable sized bet or even a check is that a good/aggressive opponent will smell weakness and come over the top of you. However, you are weak here, and you should either check/fold or make a blocking bet in hopes of a cheap river.

I like the semi-bluff on the flop but when the 10 falls on the turn you should have checked it. He might have bet small to not scare you out of the pot and you could have seen a cheap river. If he calls your raise on the flop there is a good chance he has a 10 and betting strongly on the turn is a big mistake.