I just read an excellent post by Dianne Goode, titled Remodeling Isn't As Easy As It Looks On TV. The writer makes the point that reality shows are largely staged fantasies. How many times do we have to watch somebody "almost" get devoured by a gater, or get fired, or remodel their home in an hour before we figure out that it isn't really happening? The answer is simple. Some of us will never figure it out, and some will.
There are three types of DIY undertaking, things you can probably do fairly well by yourself, things that will take you longer and cost more than hiring a professional, and things you just can't do successfully on your own.
You can probably fertilize, weed and mow your own lawn. You can probably shovel your own snow and maybe even paint the fence. You can probably change a part on the water faucet (it will take three trips to the hardware store), and perform minor maintenance on the car, like adding oil, a/c refrigerant, and maybe even change the oil.
Most household jobs that have an option of DIY or hire a professional will come in at similar cost either way, at least the first time you try DIYing them. Painting is doable, but it will be necessary to buy or rent equipment for any large scale job, and add the cost of your time if you're worth anything per hour. Electrical is also doable, but be sure to add the possibility of needing temporary housing after you burn down the house, and/or paramedics when you light up yourself with your first big mistake.
Then we get to the part where just about everyone agrees that professional help is mandatory. Building a house, major remodeling of a house, buying/selling a house, getting a divorce, and running a country are examples of activities that require professionals. Now here's the tricky part. If you have had some bad experience with contractors, don't hire a florist for your next project. Find a reputable general contractor, get references and contact all of them. If you have had some bad experience with a real estate broker in the past, don't hire a plumber. You made the mistake in hiring them, and you need to do a better job hiring the next one, and ability to fix a clogged drain is not one of the requirements. If your last divorce took you to the cleaners, well if you're going through it again, you'll never learn -- go ahead and hire a plumber. I'll leave the rest to your own consideration.
Remember, what you don't know needs professional assistance, and all professionals are not alike.