need help on end game, heads up tournament play

[JJNJustin]

I play online sitngoes and multitable tournaments, and do fairly well. I usually get close to the money or in the money. However, most of the time my cashes are towards the bottom end, i.e. the bubble, and not at the top. I feel this is mostly due to my horrible heads up and short handed nolimit tourney strategy. I feel like I am just getting raised out of too many blinds and feel too gutless to take a stand with something like K7s or J8s. Any basic simple advice would be helpful, as there may be some simple principles I am not aware of.

thanks

-J