What's the worst that can happen if you didn't have a pre-planned work strategy and dealt with situations separately as they occurred ?

In the absence of proper planning and strategy; the project will face several issues such as:

1. It will not meet the time lines.

2. Waste of resources

3. Additional cost due to delays.

4. Losing focus and interest of the team members.

5. Risk of closing the project or may be given to another team..