i sometimes work with clients on their belief systems, particular the thoughts that can darken our thinking, keep us stuck, or create fear and anxiety, thoughts that actually most of us have on a daily basis (to a greater or lesser extent).
some of these more negative type thoughts can actually be temporarily useful:
doubt can be useful as it allows us to pull back for a moment and maybe question a decision, a choice made, and then reevaluate.
there is even some use to procastination: maybe we weren’t ready to make that decision yet, and the time needed to procrastinate has allowed us to reach a ‘decision’ (though it may not have felt like this at the time). and the brain likes to feel like it is doing something (where procrastination is ‘doing’ something)
however, what happens when our negative thoughts become disabling or shade the day. it can be useful to start to identify our thinking patterns, to slow down the process, and then actively challenge them with rational thought.
this article discusses ‘the worst thing is going to happen’ and ‘i can’t handle it’:
http://www.quickanddirtytips.com/health-fitness/mental-health/the-two-big-beliefs-linked-to-anxiety