I don't think it's a pointless question at all! Why, if your arms can exert a force upwards, can't you lift yourself up? Of course, you can if you have a beam and pulley and throw a rope over the pulley and pull on it - up you go.
So, why doesn't that work if you push down? JeffM has it right - it's Newton's Law - every action has an equal and opposite reaction. In the case of the beam, the ends of the beam have an upward force applied by the wall that holds it. In the case of you just lifting yourself up, what are you pushing against? Where's the reaction? If you lift a baby up, the extra weight is transmitted through your feet and you weigh more - no surprise, you are now holding a fat, bawling infant. The increased weight is balanced by a balancing upward force from the floor. That force is what you don't have if you grab yourself by the scruff of the neck and yank up - your head may come off, but your feet will remain firmly planted and blissfully unaware of the suicidal machinations a few feet up...
We cannot lift ourselves simply because of the Newton's 3rd Law of motion. It states that "forces always occur in pairs. If an object "O" exerts a force "F" on object "A", then object "A" exerts an equal and opposite force "F" on object "O". So if you try to lift yourself, the force of gravity pulls you down using the same force you are using.
I think this question is about depression, not gravity. There is lots of help out there if I'm right about the topic. Write your thoughts out in point form or whole sentences and take it to your doctor. You don't have to say anything to start--just hand him/her the paper. Your doctor will ask you a few questions. You need to answer them. Them you can make a plan together about how approach this. Follow the doctor's instructions. If you are given a prescription, have it filled right away. Keep a logbook on how you are feeling and take it with you on subsequent visits. There is lots that can be done about depression. Increase the wattage in all your light bulbs. Get outside. Volunteer. Don't miss a doctor's appointment. Good luck with this.