With a baby, everything is complicated. Many things are going through your head even when you are doing something simple like feeding her. Where's the burp cloth? Do we have extra milk if she finishes? When did we start this bottle? How much has she already had?
If you are missing something, it'll be hard to correct when the baby starts screaming/throwing up/screaming and throwing up at the same time.
I said it last month, and I'll say it again: being a new parent has given me a lot of sympathy for my students. While defending, they have many thoughts at once: what was the auction? Did my partner signal? What was the lead again?
For both baby and bridge, a good routine can help.
It takes time to work out the routine that works for you. Don't expect to go from no plan to a perfect plan overnight. That said, It's helpful to envision the perfect flow and then take away items that are too difficult until you're ready for them.
For defending, I like a general three step plan:
1) Get as much information from the auction as you can
While you can ask for a review during the first trick, it's much better to focus while the auction is happening. Use that time while the opponents are thinking about their bids to keep track of what you know and also what you might lead based on the auction.
2) Take a look at dummy to determine what declarer's plan will be
After a lead is made (either by us or partner), analyze what declarer will use dummy for. Is there a source of tricks? Will declarer ruff something in dummy? If you know what declarer will plan on doing, you can try to stop it. While you are here, estimate how many points partner will have (40 - (your points, dummy's points, and declarer's range combined)).
3) Look at partner's play to trick one and get as much information as you can
Did partner lead fourth best? A sequence? Did partner signal attitude? What do we know about the various lengths and high cards in this suit?
Most of this requires detective work. That's what defense is about.
Once you've gone through this setup, defense will be easier. You know about a particular suit. You know roughly how many points partner has. You know what declarer will try to use dummy for. That limits the number of things to track to a manageable number.
On this deal, let's try to put it to the test.
You, West, hold:
Q1082 
A8 
9752 
875
.
With no one vul, the auction goes:
| West | North |
East (Partner) | South |
|---|---|---|---|
| 1 |
|||
| Pass | 1 |
1 |
1NT |
| Pass | 3NT | All Pass |
What will you lead?
Partner overcalled hearts, so this is an exception to the idea of "don't lead an unsupported ace". You lead the ace of hearts, and get to look at dummy.
| Vul:None Dlr: S |
DUMMY
|
|
| Q1082 A8 9752 875 |
3 |
|
| 4 |
That's dummy. We can see the first trick. What now?
Many players already have the 8 on the table. We should be reviewing the auction, we know declarer has 12-14 points and hearts stopped. Would declarer bid 1NT with just one stopper in hearts? Possibly.
We know partner has about 9 points (12 in dummy, our 6, and declarer's 13ish gives 31). The question is, where are partner's points?
We can see that declarer is going to use dummy's diamonds. If declarer has the ace of diamonds, then declarer has six diamonds and a club that we know about. Declarer must have some extra high cards as well. That doesn't necessarily mean we need to take tricks as quickly as possible, but we probably can't take too much time to find our tricks.
Now, for the most important piece: what is going on in hearts?
Partner's play of the 3 said "I don't like it". Interesting, since partner overcalled the suit. Partner does not have, say, the KQ here. Should we continue anyway?
No! We should not. Partner might have Kxxxx or even Qxxxx in some situations. While we might chide partner's poor suit for the overcall later, we shouldn't punish our score. If we don't continue hearts, what should we switch to?
Spades is our best bet. Yes, a 1 opener doesn't guarantee good clubs, but dummy's clubs are reasonably strong. Declarer might have rebid 1 with four good spades. If partner has the A or K, we'll be in good shape. If declarer has both the A and K, it was unlikely we could do anything to beat this. We might, occasionally, be giving up an extra overtrick. That's a risk to take given the probabilities.
When leading away from an honor, we should lead a low spade to tell partner to keep playing this suit. Partner wins the ace and continues spades. We can look at the full deal:
| Vul:None Dlr: S |
J9 52 KQJ643 AJ2 |
|
| Q1082 A8 9752 875 |
A743 Q10973 A 943 |
|
| K65 KJ64 108 KQ106 |
Declarer does have a spade stopper, but partner's diamond control will prevent declarer from getting enough tricks. This deal is a good example of what experts sometimes call "timing". If you continue hearts or switch to clubs, you aren't giving declarer anything they can't do themselves (although your lead did help declarer), but you lose the opportunity to knock out the spade stopper before they knock out partner's A.
This is why notrump contracts are sometimes considered a race to set up your tricks before the opponents set up their tricks. If you have a good routine, you won't be able to solve every problem, but you'll make it easier for yourself to focus on the important aspects of the play.