Self Defense is difficult to justify to twelve jurors, i.e. the court system if prosecuted. Yes, even if you firmly believe that your actions were to forestall an attack by a threat it can be determined that you stepped past the acceptable point, which is fluid by the way, of what is to be determined legal defense.
If you really want to preempt an attack it is better to preemptively avoid the entire situation or use some preemptive tactic that involves leaving, running, etc. to a safe zone. When you add in the word strike as to preemptively applied you open the door wide to a view of your "aggressive action" toward another human being. That human in this type of scenario is no longer the aggressor/threat/attacker but that has shifted from them to you.
It should be noted that witnesses, uninformed/uninitiated type, will most likely not see the "tell" that resulted in your preemptive strike but will only see you strike "first." If you hit first, you are the aggressor. If you are the aggressor then you are breaking the law - in most places U.S.