Unless you have a strong conviction that God wants you to resign, you should accept this responsibility as something He has given you. The congregation apparently felt you had the ability to serve as a deacon, and this should encourage you.
At the same time, I'm glad you're nervous and not sure if you have the ability to do it! Why do I say this? The reason is because you need God's help to do God's work, and because of your attitude you'll be much more likely to turn to Him for the help you need. If you were brimming over with self-confidence and thought you could do this job on your own strength, then you wouldn't seek God's wisdom and ask for His help.
Both you and your fellow church officers need God's wisdom -- and He will provide it if you seek it. Be grateful for this responsibility, and see it as an opportunity God has given you to serve both Christ and your congregation. The Bible says, "If any of you lacks wisdom, you should ask God, who gives generously to all without finding fault, and it will be given to you" (James 1:5).
At the same time, don't become so preoccupied with your duties that you neglect your own spiritual growth (or your family). Paul's advice to his fellow pastor Timothy applies to anyone who has been given spiritual responsibility: "Set an example for the believers in speech, in conduct, in love, in faith and in purity" (1 Timothy 4:12).