I doubt any attorney can answer this question for you with the information you provided. Aggravated assault is a second degree felony. Thus, the range of punishment is from community supervision (with and without jail time as a condition), and the prison time is from two to twenty years in the Texas Department of Corrections As you might imagine there are numerable scenarios. A lot depends on the severity of the crime. For example, someone may be charged with aggravated assault for merely threatening someone with a deadly weapon. On the hand, someone may be charged with causing serious bodily injury to a person. While being charged with the same crime the punishment would be different for each of these people.
You should contact a few criminal defense lawyers in your area and talk to them in person. Most offer a free consultation. Good luck to you.
Herman is correct - the potential sentence is a fine and from 2 to 20 years in jail. If you have never before been convicted of a felony, you are eligible for community supervision. However, eligibility does not mean you will get it. Just as Herman pointed out the differences in types of offenses that would charged as aggravated assault, the worse the offense (or injury to the complainant), the more likely you will receive some type of incarceration whether a prison sentence or a jail sentence as a condition of probation. (You can receive up to 180 days flat time in jail as a condition of probation.)
You should see counsel. And, while awaiting court, you should gather information which will help demonstrate that you were acting out of character and that you truly are a good and decent citizen such as your recent high school or college transcript, any awards or recognitions you have received, gather names, addresses, and telephone numbers of positive people without criminal histories who could provide letters of recommendation on your behalf, etc. After consulting with your lawyer, s/he may instruct you to become involved in counseling for drugs are alcohol and to attend AA or NA meetings and provide proof.