No one tests the depth of a river with both feet.
What it means
Do not test the depth of a river by stepping in with both feet. You do not know how deep you will sink. You could drown. Similarly, before you jump and commit yourself fully into anything, you should have a clear sense of the depth of what you are getting yourself into. Test it one tiny step at a time. If you jump into it without scoping it, you could drown in problems you did not expect.
