Make sure you have the proper tools and materials for the job. Research the job before hand either on the internet or buy a deceny D.I.Y manual. Allow plenty of time to perform the job and always remember saftey comes first. Do not cut corners the base work in many D.I.Y projects is what makes a good finished job.
You can do this. It's not magic. There is lots of information on the internet and there are many books about the basics of using tools and home improvement. Tackle something simple (painting might be good). Get a friend to give you encouragement and to help you solve problems.
The first thing to know is that many of these things are very rarely as scary as they may seem. There are great resources both in text and on the Internet for those who are looking to learn light do it yourself projects.