I too have a Border Collie, or Border wallie as I sometimes say. They are very intelligent and mine even makes up her own games including hiding things for me to find. True, believe it or not.
However she is also sometimes a fussy eater.
Try this.
I feed mine one good meal aday, dog meat and meal with some tasty morsels mixed in for good measure such as our left overs chicken meat, sausages ( tescos finest ) corned beef, meat gravy etc and usually after some excercise around the park.
As the other people have said they are very sensitive to your emotions, so do not be anxious or they WILL pick up on this and it will make them nervous.
Now if mine for any reason will not eat her dinner I leave her and ignor it for an hour or so, then if she still has not finnished I threaten to eat it myself. " GIVE IT TO ME. I`LL HAVE IT. MMMMMM THIS IS GOOD.
I try to push her out of the way of her dish, this is always met with barks and growls.
It`s very commical to watch and anyone who does not know dogs thinks she is very vicious when they see it done, but she has never bit anyone ever, and she is now 11.
I promise you it works every time fo me.
If your collie is active, bright eyed and happy / playful just don`t worry.
Hope this helps,
Regards, Dave H