Data management has a number of benefits, including:
This is an understandable question. You have a lot on your plate already. You have given some thought to data management, but you have limited time and you want to devote this time to the actual research.
However, writing a DMP will save you time and effort later in the research process. Nearly all of the benefits outlined above are applicable, save "meeting funder and/or institutional requirements." A well-written DMP will help you safeguard against data loss, version confusion, unclear data description, security breaches, as well prepare for the possibility of sharing data, whether this is informally to a colleague, archiving on a disciplinary or institutional data repository, or publication. Additionally, should you submit your article to a publication which has data management requirements, you will be more prepared, having already documented your processes.
The most important thing is to remember: any kind of plan is better than no plan at all. Do what you can.