I imagine that this will be a highly unpopular opinion, and I should preface this by saying that I've thoroughly enjoyed watching Pasta's progression from rookie to the player he is today. Seeing his big personality come through from day one has been cool too.
But I would seriously consider trading him for maximum value at some point in the next year or two, whilst he's in the prime age bracket. Perhaps when Marchand retires.
I think the best player comparable for him is his friend Nylander. They are very nice hockey players but it's pretty clear that this type of player can't carry the rest of the team on their back in the playoffs.
This was okay when Bergeron, Chara etc. were still around and he was a complimentary player, but now that he is 'the guy' - not so much. Seeing the team's designated best player perform with jelly legs has to impact the bench negatively.
I should reiterate that Pastrnak is generally one of my favorite players to watch, at least when the stakes aren't as high.
Feel free to kick me out of Bruins fandom for this post!