Don’t Cast Too Far.
For some reason, people equate spey rods to long casts. Sure you can cast a spey rod far but that is not the main advantage of using one. Much of the time if you are casting too far, that is a disadvantage! The real advantage is that your fly stays in the water fishing longer, you can control your swing much better with the longer rod and you can cast using much less effort and with limited room behind you.
Some spots do require a long cast to fish effectively, but not many. Most spots the fish lay out of the heavy current not far off the shoreline. When you cast way out into the fast water, the fly doesn’t sink at all. The heavy tension on it can wreck the speed of the fly when it swings into the softer holding water where the fish are more likely to be. More importantly, when you cast long the fly doesn’t swing effectively all the way in below you – meaning you aren’t even fishing the whole spot!
Finally, never underestimate the water right in front of you that can only be covered with a really short cast. The grab with only a few feet of line out is savage!