It is hard to smash your own work.
Keeping seconds and selling them or even just giving them away can be a dangerous thing to your overall career as an artist. If you are a hobby potter and don't care to ever attempt to make a living, then disregard this.
When we put forth effort and create something we tend to get glossy-eyed at the object and we see all the hard work put into it. We start looking for ways to keep it or talking ourselves into being able to get some profit out of it, because golly we put so much hard work into it we should be getting paid, right?!
Well, no, I think we are giving ourselves too much by saying we deserve that. I say smash all but your very best work. I am no leader at this, I have failed many times and now regret giving away the seconds and selling them too, even to my family. I am glad they went to a good home, but now those are the only pieces many of these people have. I have found that those who get seconds hardly ever actually buy your good pottery, and instead just hope to continue getting freebies or are satisfied with that one piece you gave them when you first started out. (This makes them sound dull or selfish or mean, but these are good people with good intentions I am talking about.) Do you see how this is dangerous? Now anytime someone comes over to their house and sees the pottery and your relatives (friends, etc.) tell them your name, you get a bad rap in those people's minds because your old junky pottery is all these new potential customers see.
On top of this, people tend to just begin expecting that you will give seconds or sell cheap pottery that "still works well" and will only come for those pieces. Your customer base will begin to build based on reasons I hope you don't care for. Pretty soon you will realize that your junky stuff only sells and your good stuff you are proud of no one really takes a whole lot of notice.
You are only as good as your weakest pot.
If you struggle with a piece and perhaps you see some potential in it, set it aside and come back to it in a couple weeks. Keep doing this until you decide it is junk and smash it or until you realize that sometimes you just needed to grow a little in your mind's eye and you have a real gem on your hands. BUT be careful, don't give yourself too much credit here and if in doubt, take a photo of it, smash it, and let it go.
One more thing. If you give someone a pot, why not give your very best to them? A gift is supposed to be something wonderful, maybe even sacrificial. You should be proud to give the pot away, and if it is a second, you can't be truly proud or it wouldn't be a second so don't give me that bull. If you give your seconds as gifts, what does that say about you and about that other person?