1. Do not give up!!!
2. Try decompose your GMAT skills: GMAT contains Verbal and Quant, Verbal contains RC, CR and SC, SC contains problems that test modifiers, ||sm, ambiguous use of pronoun, comparison, idioms and so on.
3. Take a small piece of GMAT (for example ||sm in SC) and try to build a solid background. I think you can quickly succeed in a very small part of GMAT. That will give you confidence that you are on the right beam.
4. As you will gather more pieces of studied GMAT, you will able to compose them back.
Hope this help