Niagara Falls seems to roar in my ears as I slowly try to stand up. Thousands of black spots crowd into my vision. Quickly leaning over, I tense my abdomen to try to keep from passing out.

The evening visitor who called me just moments before stands in the doorway of my dilapidated hut and chuckles. “See something interesting on the floor?” he asks with a grin.

I’m not amused. After being awake from midnight until 2 a.m. caring for an emergency patient, followed by a nonstop stream of people on my porch all day, each with some pressing need, I don’t have much humor left.

Carefully avoiding the rotten areas of the floor, I make my way to the porch and lean against the wall. After two rainy seasons, the posts supporting my house have started to give way. The whole house now leans downhill at a crazy angle forcing me to stand hunched over while the wall seems to bear down on me.

“What can I do for you?” I ask quietly.

“Well, you see it’s like this: My kids don’t like the food I brought home. Will you give me 500 pesos to buy something tasty for them?”

I sit down, trying to control my thoughts. I want to say, “Well, if you’d repay me for the three other times I loaned you money, and if you would deliver the roofing grass I bought from you a month ago, and if this weren’t the fifth time this week that you’ve come to me asking for money, then maybe I would be a little more sympathetic.” Instead, I take a deep breath and reply, “I’m sorry, I simply don’t have enough right now.”

“But my kids are crying,” he counters. “Just give me 300.”

“Sorry, I can’t,” I groan. My abdomen is beginning to cramp—a sensation that has become all too familiar over the last few months. From experience, I know I have less than a minute to get to a bathroom.

“Oh?” the man looks miffed. “You can’t?” He looks past me into my sagging hut. A single LED light I have rigged to run off a small solar panel hangs from a rafter. I can almost hear him thinking, He says he can’t give me money, but he has an electric light, and I don’t. It doesn’t matter that just yesterday this man spent his government welfare payment of 2,000 pesos on a wild spree of expensive restaurants, toys and cell phones. I have a light bulb, and he doesn’t; therefore I am culturally obligated to give him what he asks for.

“Please, just 100!” he tries again petulantly.

By this point I can barely hear him, the pain in my stomach is so intense. “Sorry, no,” I reply through gritted teeth. I’m not sure I’m going to make it to the bathroom.

Without another word, the man turns on his heel and walks away—a very rude gesture in this culture. Following him off the porch, I make a mad dash for the gulch. The only real bathroom in the village is 100 yards away. Its toilet hasn’t been flushed in two weeks because there hasn’t been any water in the village, but this hasn’t stopped the kids from filling the toilet bowl to overflowing.

I’m thankful it is nighttime and I can privately relieve myself in the gulch near the house rather than running a quarter mile to the nearest section of forest. It looks like I’ll have to start another course of the wretchedly bitter medicine prescribed for this particular type of gastrointestinal distress.

Half an hour later, I make my way back to my house, white as a sheet and trembling. A church member is waiting for me. “Brother,” he addresses me gravely, “I have something to say to you.”

“Say on,” I reply, curling up on the floor, too weak to sit.

“The entire church is angry at you and gossiping about you. You know the wood you hired Ernie to haul here to rebuild your house? Well, you gave the entire job to him instead of dividing it up a board or two to each person, so now everyone is mad at you and Ernie. That’s why no one would talk to you at prayer meeting earlier this evening. I just thought you ought to know.”

“Thank you,” I whisper.

A look of sympathy comes into his eyes. “This is just the way we are,” he says with a laugh. “This is another one of the reasons all the other missionaries who came before you either gave up or failed to reach the Tawbuid. Remember? I’ve been telling you about them. Let’s see, there’s the one who left because of continual sickness, then there’s the one who left because of a moral failing. Another simply left—we don’t know why. Another got so sick of the people always using and abusing him that he cursed us all before leaving. Let’s see, another one . . .”

“I remember,” I say holding up my hand. “I distinctly remember each missionary who failed and the reasons why. Thank you.”

“Okay, brother,” the man says with a slightly worried look on his face. “Well, you must be tired. I’ll let you rest. Good night.”

The ever-present ants have started crawling around my face and up my pants, but I am too miserable to care. Suddenly, I am overcome by a wave of nausea, and my stomach empties.

This is ridiculous! I think to myself. What have I accomplished in the two years I’ve been here? I’ve saved some lives with my medicines, but for what? To continue on as they always have? I’ve helped unify the Adventist church in this village, bring them back to a foundation of Christ and start a missionary program, but has anything else happened? Every time we get close to a breakthrough, someone gets cold feet, someone else backs out because I won’t give him a water buffalo, or everyone just stays home because they don’t feel like getting up. Missionaries have been trying to reach the highland Tawbuid since the 1950s. What makes me think I’ll succeed where they failed? Maybe I should just call it quits and go somewhere else.

The darkness creeps in around me. An ant bites my cheek, and tears well up in my eyes. The highlanders don’t even want me here. They’ve tried their best from day one to kick me out. I know from watching veteran missionaries that these diseases, if allowed to continue recurring, will break my health permanently. Is it worth it? Why should I put myself through so much misery?

But deep down inside, I already know the answer. With no one but angels to witness, I whisper into the dark, moldy night. “I have made a vow. The Lord has unmistakably called me, from my sophomore year of high school until this day, to work for the salvation of the Tawbuid. I have vowed that I will not relent until the work is accomplished or the Lord removes me from it. Those who have gone before me have shown the way, and it is a bloody, painful way. But it is the only way the Tawbuid will be reached, the Tawbuid for whom Jesus Himself bled and died. This is the real reason why I am here. Jesus suffered more than I ever could to take away the curse I deserve and give me a life of eternal happiness. And He who so loved me said, ‘Take up the cross and follow Me’ (Mark 10:21). Once again, I vow never to give up, never to back down, so long as You give me the strength to endure.”

I feel no flood of peace, no sudden deliverance. The pain and nausea continue. But as the whisper leaves my lips, I seem to hear a voice say gently, “Carry on, soldier. Carry on.”

• Twitter