Am I too soft-hearted?

In the past, sometimes , even though I haven't had much cash, if anyone asked me if I could "lend" them some money, I usually have obliged. 
Now, perhaps I being naive, but when I went to school, "lend" meant that you would get what ever item was on loan back.  I lost some very good cookery books in this way.
It's not just money, books have similarly been loaned, only for me never to see them again.
So why when I usually don't say no if someone asks for a loan of some kind do I feel guilty about asking anyone for a loan of anything, or even some help?
My point here might seem a little obscure, until I clarify things by saying that my monthly income has shrunk over the past few months, and although I knew it was coming, I didn't realise just how much income I would be down by.  I could have worked it out, just didn't think about it.  So until I get used to things, money is a bit tighter than usual.  So I don't need things happen like they did yesterday. I was driving back from getting my haircut, in the rain, when my wipers packed up on me.  I knew it wasn't the fuse due to a noise I heard prior to them ceasing to work, so I drove, very carefully to the garage where I take my car, as it was closer than home on my journey.  A rod has "come off" or snapped, I don't know which, and it is going to cost around £40-£50.  I do have the money, but I like to keep a "safety net" in my bank account, in case of emergencies.  Ah, well. 
Back to the original point.  I did lend someone around £500, which they promised they would pay back.  I could really do with it now, it would make things a lot easier, but I think they have forgotten completely.
Right now I am telling myself I will never loan anyone anything again, but I know deep down I probably will, given the right circumstances