Use of event handler is always recommended, and it is the safest way to modify any existing functionality in Dynamics 365 for Finance and Operations. However, it may not fit with every requirement, but always try to use event handler in every possible place. You can use event handler on Classes, Forms, and Tables. On any method, whether it's on a Table, Class, or Form, you can write pre or post event handler, while on Tables and Forms you will also get standard Events under Event nodes such as onInserting, onDeleted, and so on.
To understand this concept better, let's take the example of General Journal. While entering new lines in Journal, we need to validate that the credit amount must not exceed 1000. To do this, carry on with the following recipe.