The Lord said to me, "Son of man, stand up on your feet and I will speak to you." As he spoke, the Spirit came into me and raised me to my feet, and I heard him speaking to me.
He said: "Son of Man, I am sending you to the Israelites, to a rebellious nation that has rebelled against me: they and their fathers have been in revolt against me to this very day. The people to whom I am sending you are obstinate and stubborn. Say to them. 'This is what the Sovereign Lord says.' And whether they listen or fail to listen--for they are a rebellious house--they will know that a prophet has been among them. And you, son of man, do not be afraid of them or their words. Do not be afraid, through briers and thorns are all around you and you live among scorpions. Do not be afraid of what they say or be terrified by them, though they are a rebellious house. You must speak my words to them, whether they listen or fail to listen, for they are rebellious. But you, son of man, listen to what I say to you. Do not rebel like that rebellious house; open your mouth and eat what I give you."
Then I looked, and I saw a hand stretched out to me. In it was a scroll which he unrolled before me. On both sides of it were written words of lament and mourning and woe.
And he said to me, "Son of man, eat what is before you, eat this scroll; then go and speak to the house of Israel." So I ate it, and it tasted as sweet as honey in my mouth." (Ezekiel 2:1-3:3, NIV)
When God calls us, God does not call us to a result. God calls us to obedience. When God called Ezekiel in this passage, God did not want Ezekiel to be concerned with whether or not the people liked him, or even whether they listened to him. God wanted Ezekiel to be obedient and deliver God's messages.
When God calls us to a particular life of service, all God wants us to be concerned with is obedience. Whether people respond to the message God gives us or the love we demonstrate is beyond our control. All we can control is whether or not we are obedient and whether or not we hold back out of fear. At times, God calls us to very scary places, but even there we are expected to obey ("though briers and thorns are all around you and you live among scorpions…")
Whatever life God has called you to, stop worrying about whether or not you will be "successful." Stop worrying about whether people will listen to you, much less respond to you. Stop worrying about whether or not you will even survive. None of those things are ultimately our concern. Our concern should be obeying God and trusting God enough to do so.
Whatever God has called you to, are you willing to live that life in obedience or are you paralyzed by questions and fears? God has promised to never leave us and never forsake us. The only question is, do you trust Him? If you can, there will come a time when the task God has assigned will taste "as sweet as honey" in your mouth.