Think it is normal to have cold feet, BUT it is big commitment to have a pup when there is just one of you.
Both myself and the OH work full time, although I am 5 mins from work and home for lunch. The OH does not come home during the working day. We have taken on 2 puppies in the last 18 months. The eldest Tia is now 17 months and our 2nd one Jake is now 4.5 months. We have been very lucky and having a week off when we first got the pups was all it took to get them into a routine of being left for up to 4 hours. I have to say though, I felt exhausted some days and barely seemed to get time to get my lunch when we first got Tia and again when we got Jake (but only a week or two with Jake).
OH is on a course away this week and it's very tying having a dog on your own, it is not fair at all to leave the dog on an evening when you have been at work that day (in my opinion) and we have a rule not doing this. I'm expecting to be totally cream krackered by the end of this week!
We do a mix of hols and weekend away now, some with the dogs and some without. You need to find a place you are happy to leave your dog, there are many kennels now which are not kennels as such and you dog lives with the people in their home. Our two go to a farm where they have a few dogs at a time, it does take some planning though and just having to say no to last minute things sometimes.
I hate to "rain on your parade" but it will be very hard work on your own with a puppy, but if you are 100% sure and totally committed you could make it work. Are you a very patient person? If you are not a patient person you may find it very difficult at times, puppies need lots of patience and again it's harder to be like that on your own (in my opinion).
I really hope you come to the right decision for you, it's great that you are thinking it over so well. If you are having serious doubts then maybe you need to give it a few months and see how you feel then?