as a fighting game fan all i can say is practice more at the game. There has been lots of juggling in Tekken so if your afraid of getting trapped in it work on your defences. Many mistakes people make in tekken is going all out offence. If your serious about getting better then check out some tourney players or character tutorials on how to control them better.
as for SF....its actually very easy to beat a person spamming the same move. They become predictable and you need to learn to use the tools givin to you and respond to it.
I suggest playing casual matches and practice more on your defencST and reading opponents. Good fighting games are like a chess game.