What hands actually win?
"You gotta know when to hold 'em, know when to fold 'em, know when to walk away, know when to run" Kenny Rogers
It can be shown from collected data that on a table of six, 46% of the time a hand value of 21 will take the pot and 37% of the time a hand value of 20 will take it. What does that mean? That means on a table of six 83% of the time anything less than 20 is worthless. In fact if you stick on 17 only 1% of the time will it turn out to be the winning hand if you reach the showdown. Add a nickel to your 17 and you have enough for a hot cup of jack squat.
These statistics change as the number of players drop i.e. on a table of five 20 or above wins 78% of the time at showdown, however this is still a valuable rough guide.
Although you can always bluff and there is plenty room for judgment my recommendation to you is to only play on a hand with a value of 20 or 21 with a table of 6 most of the time.