I have the same problem you have (namely work gets in the way of trading). During my very brief (3-4months) forex trading history, I've noticed that even though Asia market opens at 6pm, nothing really major happens normally until Europe market opens around 2am. Then there is also a ton of activity in the morning when US market opens. So bottom line, if you're trying to scalp you're better off losing some sleep or showing up to work late.
Neither of those options was working out for me so I switched to more of a swing-trading philosophy the last couple of months and it's been working great (on a
demo account) so far (I made about 30% in 6 weeks). I basically analyze the daily charts to determine support/resisitance and trend and enter a position accordingly. Since this is swing-trading, I set target much higher profits (and set much larger SL) than with scalping-type day-trading. Also I try to stay interest positive at all times so that if the trade goes against me I can just collect interest for a few days and wait for it to reverse (note I'm using O A N D A which pays/receives interest constantly). I've mainly been making good money with the major USD pairs (USD/JPY, EUR/USD). I have also done well with EUR/GBP because it seems to stay in a pretty well-defined range. Another month or 2 of good returns and I'll put some real money into this game.
Oh yeah, the other advantage of the swing-trading approach is that you don't have to be glued to your monitor like you do when day-trading.