Winter blues

For a few weeks I've been feeling a little lower than normal. It's not depression but a lot of the time I'd describe myself as a bit negative.
And it is getting to me.
It is clear to me that the biggest issue I have is that I worry too much and that is a big part of this lower mood as I tend to allow what most people would deem minor things become potentially major. Mountains and molehills and all that.
This became apparent yet again today as I felt crummy for most of the day and spent too much time and energy over analysing what was going on.
I'm far too sensitive to what the body is up to and as a result the imagination starts running. I wish there was a button I could push that will stop the times of worry.
I know that it is a battle I have to fight harder, to condition myself not to get caught up in `what if' and everything else that goes with it.
Is it as easy as saying to yourself `I won't worry today' or something to that effect? Like everyone else I want an easy fix but I realise it ain't going to happen like that. They don't call it the hard way for nothing!