LOSE vs. LOOSE
It's quite the common and understandable error to make, especially while typing, but it stumps me that I never see anyone mistake "desert" and "dessert". We take our after dinner snacks seriously, I suppose.
The difference between "lose" and "loose" is that "to lose" is a verb, while "loose" is an adjective. To lose an item means that is cannot be found, is misplaced, or out of sight. And item can be loose when it is over-sized, ill-fitting and not tight. One way to remember the difference is the extra "o" in loose; think of it as being too much, like too much fabric in a loose fitting shirt.
It would be a good idea to get fit, but don't lose too much weight or your clothes will be too loose!