How Do I Keep My Patience with My Four-year-old?

When I was pregnant with my 2nd child... my daughter was 3.
I spent "my" pregnancy on HER. Meaning, I spent it on her and talking with her... and "prepping" her for her upcoming Sibling. So that, once her baby brother came home, she was not in a shock. Because of that, once baby brother was born and came home... she adjusted like a Champ.

While I was pregnant with my 2nd, me and my daughter took photos of her and my growing belly... She sang and talked to her baby brother in my belly, she "helped" me imagine what baby brother would be like, she even came with me to my Pre-natal appointments (which my Doc encouraged) and my Doc even taught her how to put the Doppler monitor on my belly to hear the heartbeat etc.
AND.. .when I was pregnant, I explained to her that Mommy needs to rest... Mommy will get tired, Mommy cannot carry you etc. I explained to her in a loving way and in a way that she could understand.
AND we would take naps, TOGETHER everyday.
I explained to her, how as my tummy gets bigger... I will not be able to RUN or move around as quickly etc.
She understood.
It really helped her, that I prepped her for her baby sibling, while I was pregnant. And we actually bonded VERY well, while I was pregnant.
I told her that she will always be my first baby... Mommy is always there for you... but Mommy will be busier. But so we made up our own special handshake and gesture.... so that, if I was nursing baby and or baby was sleeping... she could "signal" to me anytime, and she still felt special.

I also, each month, explained to her how her baby brother was changing.
I explained to her that:
babies cry
Mommy nurses him just like I did with her
MOMMY takes care of baby, she does not have to worry.
Baby is not like her nor knows things like she does etc
And each month, or when her baby brother was teething or going through hard stages... I'd explain to my daughter about how it is normal and that is what babies do. Thus, she never got frustrated with her baby brother. And she never felt, jealous.

And, I also explained to my daughter... that just because she is the older child... Mommy will NEVER expect her to act older, because she is still a young child herself. She is herself. And to always tell me how she feels or if things are bothering her. So that, she does not feel stressed or resentful of her baby sibling.
I also made sure, to tell my daughter, that I will NEVER use her... as an "example" for her younger sibling, nor compare her. In other words, she is a child herself and she is not expected to be perfect nor to suddenly grow up. She is just a little kid herself.

My daughter and I, really bonded... while I was pregnant with my 2nd child. It was real special. If/when I was tired or grumpy... I always explained to her. Or I would say "The Doctor says Mommy has to rest... keep me company? Lie down by Mommy..." and she really enjoyed that.
My daughter was 3 at the time, not an easy age. But I tried to understand, that her life and Mommy being pregnant... was about HER life changing. But because she is a little child... I needed to help her.

It's the hormones. But you have some fabulously, magnificent advice fro SH down below. She hit the nail on the head. For as much as WE are the pregnant ones, it's really about the existing little ones awaiting a new baby too. Follow that sound advice, it'll work magic between you and your son.

It's hard! You have a lot on your plate, and even your body isn't cooperating as well as you'd like it to (with justification!). You're tired, you may be feeling squeamish, and your fuse is a little shorter than usual.

But you're taking responsibility for the situation, which shows that you're still the grownup.

You can do one of two things when someone behaves in a frustrating way - whether that person is four or forty: you can react (a knee-jerk, emotional thing) or you can respond (putting your mind in gear before the mouth gets in there first). Responding is better.

I had to do at least three things. First, I had to do the proverbial "count to ten" routine, making sure I breathed as I counted! (Otherwise, I might hold my breath and just wait to explode.) Second - and I wish I'd done this better - every time I had to correct one of my young children, I'd try to praise that child at least *three* times. It helped me not to let my emotions take over.

Third, I would stop what I was doing during the day and take a good long look at that child. I wouldn't just look, I'd SEE. I'd remember how precious that child really is. It really did help.

I found it also helped to take breaks during the day and read with the little one(s). The noise level in the house lowered considerably, and it was easy to rest with my feet up. We read lots and lots of books when I was pregnant!

It's going to be hard to do anything proactively if you don't notice it coming on. However, if it happens, just make sure you apologize and tell him that you overreacted because you're tired. I've been doing it with my 3 1/2 year old and I'm not pregnant, so I don't have a good excuse. She tells me it's okay and gives me a hug after, though. :)

I love S.H.'s answer. Right on target.

I was going to suggest spending some deliberate time every day thinking through what your daughter's experiences will be like, having you more distracted and devoting your time and energies to the new baby-to-come. Be close to her, really see her and hear her. I think you'll find you feel "softer" around her, and control will be less of a problem.

Congratulations! My best to your family.

Take a break now and then-come back fresh and you will have more patience.

Hmm, just reading the subject, my thought was, "Have a martini... or three..." but seeing as how you're pregnant, I guess you can't really do that. In this instance, maybe take a deep breath, walk away for a moment and count to ten before you snap at him. It's hard to do, because 4 can be a tricky age, and pregnancy hormones will drive you nuts. Just remember that you need to pace yourself, too. Even though you're not obviously pregnant to any outside observer, your body is still going to run out of energy before it used to. Just do your best to take a breather before you really think you need to. That will help you keep your temper when dealing with your little guy.

Congratulations on your pregnancy!