I have two sons with a 2 year age gap. My youngest just 12 weeks today!
Some things come as a nice surprise...like how quickly you can adapt, and get into the swing of feeding (bf for me, was incredibly difficult first time round) and having octopus arms and multi tasking and sharing your love between two beautiful children.
The moments when your first born starts accepting the new addition and gives them little kisses and strokes and hugs....your heart will explode.
It's ok to find it really hard. And not enjoy maternity leave all that much. I'm struggling with this, lots of people thinking I'm off swanning about living the life of Riley and it's quite the opposite. I find it helpful to just be honest with people.
Accept all the help that is offered!!!
Another tip that helps me personally is trying to get a shower/dressed/makeup for the day done before the two boys are up. This means getting up a bit earlier (precious sleep I know) and will only work when you kind of have a semi-predictable wake up time for baby (it does eventually come) But I just find it gives me a huuuge head start for the day. I don't need to worry about trying to get ready in between giving one breakfast and bf the youngest or whatever. You can just run out the door once the kids are sorted.
On that note - get out and about! Staying in might drive you mad. But again that's personal preference.
Meeting other mums with multiple children/similar aged really helps too.
Out n about double is amazing - just got one 2nd hand and no your 2 yo will not walk lol
Invest in a good baby carrier/sling if you havnt already got. Ergo baby 360 is great! Very comfortable!
Lastly enjoy it!! Suck in all that beautiful newborn stage of velvety heads and beautiful baby cuddles.