Noooo folding is not good.
Think of these things:
1. sometimes villain gives up river with a draw and you win
2. sometimes you hit an ace or jack and checkback and win
3. sometimes you hit your flush and villain has a set/2pair/flush or continues
bluffing a straight draw and you make more money
So - lets look at how much money we need to make to justify calling turn.
_____________________
Turn: 3Diamond ($59.48, 2 pla
yers)
UTG+1 bets $42, stttNNN folds
_____________________
So calling 42$ into a pot that will be 143.48$.
Lets make some assumptions (gonna start with bad ones for you to show how not close this spot is).
46 cards left in the deck, 9 make you a flush and 6 a pair, so 31 blank rivers.
Here I want to treat 7,8,Q differently than rest of deck.
So on the 23 non 7,8,Q rivers lets say you always lose for an ev of -42$
On 7,8,Q I think villain's will bluff less, so lets say you win 10% of the time on those 8 rivers. Winning 10% of 143.48$ is 14.35, so our ev here is -27.65$
On an ace or jack river it's hard to estimate what exactly will happen. I think assuming on ace river we win ~half the pot, and on a jack river we win 10% of the pot would be reasonable. I'm assuming you fold to a bet and checkdown and lose most of the time on a jack, and that on the ace you fold to a bet but checkdown and win.
So for the 3 aces we win 50% of the pot for 71.74$ and an ev of 29.74$.
For the 3 jacks we win the same as on the 7,8,Q so lose -27.65$.
So far doesn't look good 
So I'm going to sum all of this up and see how much we need to make on average when hitting a flush to make up for what we lose the rest of the time.
(23/45*(-42)+8/45*(-27.65)+3/45*(29.74)+3/45*(-27.65))= -26.24
So if x is how much we win when we hit a flush, to breakeven on a turn call we'd need:
(x-42)*9/45=-26.4--->x=140.4
So... when hitting your flush you'd need to win a pot that's bigger than 140.4 in order to profit. Given that after our call the pot is already bigger, this becomes a very easy and very profitable call.
