As an experienced engineer I can tell you maintaining good grades does not increase your chances of a job. Most employees will look at your experience rather than your marks, unless of course you go for a research position. Even then, research is a very small market, so don't bet your money on getting good academic grades.
You should use the time you have in university to get as much experience as you can, whether its paid or non-paid experience. Joining Toastmasters would also help to improve your presentation skills as you would be expected to give a presentation at some point in your degree or career