It's easy to accidentally take on more work than you can handle or to take work on with the caveat that you might not really complete it on time. Blog DivineBytes suggests that you take a look at your language and watch out for the phrase "I will try to" as an indication that you're setting yourself up for failure.
The suggestion is that "I will try to" leads to failure because it makes failure an option you can take. DivineBytes explains:
I've been using that word "trying" for years to mean that I will eventually get there; that I'm a humble man and it's not right to be too confident; and that only a crazy person can be so certain of a result. But the word itself has connotations of failure. The word "try" suggests that failure may be an option. It suggests that excuses may be imminent. It implies that once the circumstances change, I no longer am responsible for the outcome. However, not using the word "try" doesn't imply certainty of success, it implies certainty of action.
It's also worth noting that "I will try to" is probably a good indication that you're taking on too much. If you find yourself uttering those words to your boss, then it might be time to consider why you don't feel like you can do it.
Failure is not an option [DivineBytes]