So I've been playing this game for a while now and only just realised I may have made a huge mistake.

We've been playing when you go into an engagement, you must come out of it with a focus token on you from striking, whether or not you could actually strike. To put this as an example, Luke goes into attack against an AT-ST commander, dark side wins edge, luke gets tactics'd. What we would then do is put another focus token on Luke, as he has gone into an engagement and so must 'strike' even if he is already exhausted by tactics.

What this has meant in playing is a certain caution when putting in units into tactics fights, just because a tactics icon could potentially remove one of your characters for two turns, due to getting a tactics icon and then 'striking'.

Is this wrong? Have i been playing every game so far terribly afraid of tactics icons for no particular reasons?

I only say this as for a joke I drunkenly pretended to read the rule book, and page 22 has an example of a fight, in which Vader and Red five are both tactics'd and neither get double focused for being tactics'd and then 'striking'.

Cheers

In the example on page 22 Vader does not strike since he was exhausted by the tactics icon from the Twi'lek Loyalist before he got the chance to strike, same thing happens to Red Five as it receives a tactics incon from the Interrogation Droid.

Tactics icons prevent the opposing unit from striking so you would not leave with two focus tokens in that example. But if Vader had struck first and not killed the Twi'lek Loyalist then he could have received a second focus token, not that it matters since Vader is elite.

In the example you gave, Luke would not strike as he is already exhausted. Only ready units can strike as per the rules on page 20

resolving a strike
To resolve a strike, a player follows these steps in order.
1. He chooses one of his participating ready units.
2. He focuses the unit to strike (i.e. places a focus
token on the card).
3. He resolves the striking unit’s combat icons by type

Agree with Toqtamish. One minor terminology quibble though (because being loose with terminology can sometimes confuse people): Tactics icons do not prevent units from striking, nor do units receive tactics icons from strikes. Tactics icons allow you to place focus tokens on opposing units and having focus tokens prevent units from striking. This is true no matter how the focus token ends up there (having already struck, tactics, Jedi Mind Trick, A Disturbance in the Force, etc). Removing focus tokens during the Resolve Strikes part of an engagement will allow (and require) that unit to strike again before the engagement can move on to the Reward Unopposed step.