Same verse.  "Fight the good fight of faith, lay hold on eternal life, whereunto you are also called and have professed a good profession before many witnesses."

Faith is some thing you "have".  Sometimes it may be stronger than other times but once you profess it, you keep on professing it.  You "lay hold" on your faith that Christ is risen.  And has promised you eternal life because of your faith.  You continue to profess your faith in a good way--a good profession.  And you continue to do this before the world.  Before many witnesses.

In Mark 9:17-24 a man brings his epileptic son to Jesus and tells him that Christs' disciples hadn't been able to help the boy.  Jesus asks him how long his son has been this way and the man says since childhood.   Then in verse 23-24 :Jesus said unto him, "If you can believe, all things are possible to him that believes.  And straightway the father of the child cried out, and said with tears,  Lord, I believe; help thou my unbelief."

I love this scripture. ( I don't think anyone but Mark records this man's answer.)   He wants to be a believer.  He wants to have faith.  And he wants Jesus to help him believe the unbelievable.  That is the perfect example of faith.  He comes to the right person:  Jesus.  He asks the right question: Will you help me.  And he knows that the answer to his question will be dependent his own personal faith.  He weeps.  He believes.  He asks Jesus to help him with the parts of believing that he lacks.  He realizes that he himself must be healed by faith before his son can be healed.  What a beautiful story of faith.

We start with a little faith: we fight the good fight of faith.  And as we exercise our faith, it grows stronger.  Like doing push-ups for your soul.