I don't like to buy things.

I don't think it's surprising that I'm fairly careful with my purchases.  I don't splurge on wants very often, although I can understand that it takes time to overcome emotional spending.  Instead, most of my every day purchases are food (good quality food, but still food from a grocery store such that I can make my own meals).  Frugality is a clear way of life for a number of people interested in personal finance.  However, sometimes things come up that can disagree with that frugal nature.  Right now I'm struggling to justify to myself that there are a couple of things that are really worth my time, money and attention.

1. A new prescription for my glasses.  It's been about two years since I last went to the eye doctor.  I HATE going to the eye doctor even more than I hate moving.  I know a lot of people avoid the dentist with a similar level of dislike, but for me, it's the eye doctor.  I have a fear of things near my eyes and have passed out on more than one occasion when they do the glaucoma test (the pressure test where they blow air into your eye...).  I need to suck it up and schedule an appointment.
2. A new bike.  I have a bike, I shouldn't be wasting money on a better bike... right?  Except that I ride my bike basically every day (since I have no car).  I bought my bike used a couple of years ago and it is a bit too small for me and is in need of serious maintenance.  (It squeaks in the highest gear, the kick stand is about to fall off, the rear tire needs to be filled at least weekly, etc and while all of these things are definitely doable I haven't found the time or energy to actually DO anything about them.  That's not true, I replaced the tube in the tire that leaks a few months ago but somehow that didn't fix the problem.  I still don't understand what's going on there.  Any tips?)  I think the better, more permanent solution is to buy a new (possibly used) bike that is a better commuting bike, fits me, and is generally in better shape.  (Speaking of bikes, I found this post about bike ownership (from MrMoneyMustache) particularly funny.  I've actually been on the receiving end of a similar rant before I bought my bike used.  Some guy couldn't understand that I didn't have a bike.  It was on my list of things to buy, I was just waiting to save up the money.  Stills seems reasonable to me...)
3. Speaking of bikes, now that I've moved further away from campus and I'm riding more often I should really buy a new set of bike lights.  My rear light is having an electrical problem (that I can't fix) and turns off half way through my ride.  And I've been using a headlamp instead of a real bike lamp (which also needs new batteries).  I also won't be forced to ride at night until winter, so it's more of a convenience problem right now than it is a safety problem.
4. New socks.   My laundry schedule is being dictated by running out of socks.  Most of them have holes in them and have worn out, but I haven't gotten around to this so I keep wearing socks with holes.  This is just getting silly.  I bought socks after writing this post.  I'm pretty happy about that!
5. New climbing shoes.  This isn't even a purchase that I'd have to spend money on.  I have a money on a gift card and my dividend to REI which would cover this completely.  Again, I just haven't gotten around to it.  My left shoe has a hole in the toe that is growing.

Part of this is that being busy (as a graduate student) keeps me from going shopping.  I'm generally busy enough to stay away from stores other than for groceries.  However, there is also a side of me that doesn't want to give away my money when I know it can wait.  None of these things is an emergency, however they also aren't things that are unreasonable wants.  How do you decide when it's time to buy things that you can keep putting off?  Do you have to justify your purchases to yourself and if not, how do you know you are not spending frivolously?  Where is that line for you and how did you draw it?