Its a bit like smoking though its hard, I need to sort it out though, as the late nights probably are affecting me.
Yep, again I know exactly what you mean... Coffee itself can turn into a habit. I'd suggest tho not having Coffee in the house, or buying decaffeinated so you can trick your mind into thinking its getting your caffeine hit.
The thing about drinks like Coffee is they doesn't really quench your thirst but increases it, also it ruins any chance of proper concentration and makes you fidgety - I'm no doctor but I believe it to be true due to my own anecdotal evidence.
How much water do you drink a day? Just plain old tap water? You're meant to get 8 litre's into your body a day, of which a couple of litres will come from food but you really need to drink more water. (Remember drinking coffee makes you pee more, losing more water than normal!

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Also, do you eat Breakfast? - it might seem like a silly question, but I wouldn't be surprised if you said no, but you did have a cup of coffee in the mornings. Because I think sometimes we substitute eating with having a hot drink because for a short while you won't feel hungry anymore... Again I think this is true because it happened to me - sometimes drinking 3 cups of coffee in a single morning.
The downside is you're not taking in the energy you need to burn that day, which will make you feel lethargic. When they say breakfast is the most important meal of the day its true so feed your brain.
I'm starting to sound like that nutter Gillian McKeith !
In no way at all am I one of those people "my body is my temple", I mean you'll never find me eating blackberry's and nuts

but in the end I realised it was lifestyle choices to blame.
Alarm Clocks are a must if you're a night-owl, because otherwise you'll awake later, then goto sleep later, and this drifts so eventually you awake at 10am, sleep at 4am, then awake at 11am, sleep at 5am etc etc until you're completely out of sync with the world. So set an alarm clock, and even if you do stay awake until 4am one day, wake up on the dot no matter how tired you're, because that night you'll sleep earlier and put yourself back on track timewise.
Also don't go to bed with issues on the brain! Apparently one of the reasons some people are insomniacs is because of an very active brain, which can be because you're whirling around an idea, a worry or something else in your head. Instead, sit down for at least an hour before sleeping, watch a boring movie or whatever, but get yourself into a more calmer mode - beer helps lol....
I am convinced business is down because of the financial situation but it is my fault for not doing something about it.
I am hopefully going to pick up £90 for a job I have just done so if he pays me (and is not a conning robber) that money can go some where towards my business.
You really need to look at your practices.... As I mean why are you picking up this money today? Why are you worried about getting paid? This isn't right mate and you need to change stance. I use to value each hour, so if I had to take an hour out to pick up £90 I've actually lost 50% because I had to do it. Thats the nitty gritty of it - time at my PC = profit, time pissing around collecting money = wasted time.
Sometimes in IT we bend over backwards to oblige the client, but you're a one-man-band and don't have the support to undertake this. I remember you saying you had 700 clients - out of those 700, which jobs took the longest? And which were the most profitable?
Instead of support, look to services, as its a much better money spinner.
I know this will sound harsh, but just drop the clients which are taking up an adverse amount of time compared to the profit... A saying I remember is
80% of your profits will come from 20% of your clients. That 20% is your main market - the rest are a waste of time and you ever need to increase your prices or drop them completely.
Whatever you do, don't keep dropping your prices just to win the job, its not worth it in the end. In fact I thought it was such a waste of time I changed sectors completely, but thats another story and another decision for you.