One of my big rules for camping in the UK with it's changeable weather, never assume that your rucksack is waterproof. Doesn't matter how much you spent on it just assume it's going to take in water. Use dry bags to make sure your gear stays dry. I have one for the main section of my rucksack with smaller ones for the pockets.
Get a waterproof phone case, ideally the type where you can operate it while in the bag. If you have to dig about inside a dry bag to find it then it will get wet while it's out or you risk dropping it in some wet/muddy stuff. If your phone is your lifeline...make sure you protect it.
I keep an 'emergency only' set of lightweight clothes rolled and packed tightly in a dry bag in my pack which only get used when things go real bad. A light t-shirt, pullover fleece, lightweight trousers and warm socks. An absolute lifesaver if you get soaked and give you the opportunity to get changed and dry your gear without compromising your sleep kit although generally if I get to the stage of using my emergency kit, it's probably best to pack up and go.
During the day, I use my 'day kit' and dry it off when I can...at night I kip in lightweight fleece thermals which get fired back into a dry bag as soon as I'm up and dressed. Lightweigh and quick drying is always a good idea.
Try not to get wet in the first place if you can. Use waterproofs when you need to, I'd recommend ex army goretex as robust, cheap and effective.
A little discomfort can 'build character' but a lot of discomfort can drain your resolve and put you at real risk.
Lastly, don't be afraid to go home (or find a travel lodge and/or a pub with real ale and log fire). Pushing your limits is to test your skills is one thing but it's also about recognising when your limit has been reached.
Finally, savour your return.... As much as you enjoy being out amongst the green stuff that warm bath, hot chocolate/cold beer/peaty malt and warm slippers feel even better when you get home...
