1/11/12 Trade Results: 1 trade, $100 profit. How to know when a trend ends

I have my first day of class for this semester, so I'm taking the trading day light today. I had 2 signals prior to the one that I took. There were both 5 min trend signals which would have met reasonable targets. I however only took the 3rd signal of the day which was a 123 EOT on the 50 tick that had a larger price structure agreement, Bull Channel - Price @ resistance of bull channel. The entry signal was pin pointed on the 50 tick, taking a 123 short.

The chart below shows all of my reasoning behind the position that was taken, I explain below the chart:

Price structure is a bull channel. The red triangle is the "SELL ZONE" based on the price structure. I use it for targets on longs and look for short opportunities. I entered using the 50 tick, pin pointing my entry (chart below). I take profit at either a price structure zone, significant swing, or dynamic support/resistance; whichever is closer to current price / more conservative. In this case, it was the dynamic support because the next major swing was 2354.25 and the price structure support was around that level as well.