So flee youthful passions and pursue righteousness, faith, love, and peace along with those who call on the LORD with a pure heart.
This acknowledges that there are other things that will draw us away from God.
It's interesting to me that when I heard "youthful passions" I thought of indulgence in selfish desires seeking comfort, luxury, debauchery, etc. I think that certainly applies, but the most clear thing he is referencing in context is a quarrelsome spirit.
Earlier in verse 14:
Keep reminding them of these things. Warn them before God against quarreling about words. It is of no value, and only ruins those who listen.
and 23, the verse directly following:
Don't have anything to do with foolish and stupid arguments, because you know they produce quarrels.
Probably the two things that sank in deepest as I thought about this verse more was first the call to action to flee. Seeking God takes action. Escaping youthful passions takes action.
The second thing was how important it is that we pursue God with other people, and not just with anyone, but specifically with people who call on the LORD with a pure heart. I think that means simply people who are genuinely pursuing God with their whole heart.
Like many verses, this sounds simple, but are you actually doing it? Are you actively fleeing sin and pursuing God instead? Are you seeking God with other people who are doing the same, sincerely seeking God with their whole heart?