It does not matter that when you first start going to a gym (or even if you have been going to a gym for awhile) that you are only able to lift the lightest weights or use the aerobics machines on their lowest settings.
What matters is that you are making an effort. The lightest weights lifted are still heavier than a bag of chips and a cola. The lowest setting on any of the aerobics machines will still lap anyone slouching out on a couch.
Yoda was wrong, there is value in "try". Try until you achieve "do". That's how it's done.
That is how you work your way to improvement. Making an effort requires trying. You may only be able to slightly budge the weight today, but after a little consistent effort, after a few weeks or months of persistently trying, you will be lifting that weight as if it were a feather. You will have reached the "do".