Internal evaluation can be an excellent way to check the quality of one's work, to track progress (in programmes or projects, for instance) and to gather information for management decisions and longer-term learning. To make the most of such exercises, they should go beyond self-reflection. Especially for small to medium-sized teams or organisations, sitting around a table and contemplating one's strengths and weaknesses, as well as successes and failures, is a good start, but just not enough.
Things you can do to gather more insights and make the most of them:
If you regularly collect and document information from partner organisations, clients or other people involved in or affected by your work, use it! Use it to find out whether the activities you and your partners carry out do - or are likely to - contribute to the goals you pursue. Use it also to examine - or read between the lines - how the quality of your organisation's work is perceived.
You can also bring such information to a "data party" with people outside your organisation - for instance, some of those who are supposed to benefit from your projects, or else external specialists in the field you work in. The idea is to make sense of the information from your projects/activities together, every participant with their own perspective. (Obviously, you will have to make sure data are sufficiently aggregated and anonymised so as to avoid violating anybody's privacy.)
If you don't continuously gather information from those involved in your projects/activities, then you can carry out your internal reflection in stages - for instance, (1) you decide together which questions (a handful at most!) your internal evaluation should answer, and (2) then you allow for a few week's time to gather information - for instance, in conversations with stakeholders and external persons, just like an external consultant would do in a "qualitative" evaluation.
If you don't have time for that, you can replace item (2) by a consultation bringing together people who are directly involved or affected by your work. Here, external facilitation can help create an atmosphere and a work flow that enables everyone to openly share their experience and their perceptions of your organisation's work.
Both approaches take more time than a simple half-day workshop of navel-gazing. There is nothing wrong with workshops or short retreats - any break from a busy work routine can be beneficial. But involving others will multiply your chances to gather precious new insights. Try it out!