Two of the biggest stressors for DIYers are projects that cost too much or take too long. Unfortunately, there’s no sure way to guarantee that one or the other (or both) won’t happen. But there is a lot you can do to minimize the probability.

When budgeting, a big mistake DIYers make is not considering the little things. For example, you might budget for drywall panels but neglect to include the cost of nails, tape and plaster. It’s easy to overlook these small items thinking they won’t add up to much of an expense. But often they do. In fact, for many renovation projects, the little things account for up to 20% of the cost.

Another expense that is often overlooked is taxes. When you find a bathtub you like for $399, be sure to budget for what you’ll actually pay out-of-pocket. Also, don’t forget possible delivery expenses.

A budgeting tip many experts recommend is to price everything you need and then add 10%. That gives you a buffer.

Regarding scheduling, consider whether or not you’ve done this type of project before. If you’re laying hardwood floors for the first time, there’s a learning curve. You’ll likely take two or three times longer than you would if you were more experienced.

Even if you have experience with the type of project you’re undertaking, it’s human nature to underestimate how long it will take. So, if you feel confident you can install that sink in an hour, give yourself two.A lot of this, of course, is common sense. But if you take a common sense — rather than an optimistic — approach to budgeting and scheduling, you’ll stand a much better chance of your DIY project going smoothly.