1. A supposedly fun thing I'll never do again
I'll be the first to admit that often when I volunteer, the ideal of volunteering always seems more attractive than the reality of actually doing it. Like luxury cruises and eating four plates of food at Thanksgiving, volunteering is one of those things that really can be too much of a good thing. Better to avoid doing anything that overwhelms you with significance. Spend a week on a mission trip with a group from church, and you might come back exhausted, far too familiar with what socks smell like that haven't been laundered for a week, and hyper-aware of how good things are for you, really.
2. Like the sacred heart of Jesus, your heart might break
Offering our time in places we might not otherwise go hurts our hearts. We are exposed to human pain--loneliness, illness, imprisonment, anxiety, loss--and we are reminded of our own pain, and reminded how much of human pain in the world we have not busied ourselves alleviating. We are, in fact, reminded how much human pain in the world we are incapable of alleviating. Today, for example, while singing at the Veterans Home, our Sunday school youth met many men with forms of dementia that cannot be healed this side of the eschaton. It's hard to simply spend time with them. You/we want to do something, fix something. If we can't do something, or fix something, why are we there? Then crack, your heart breaks and pours out, both to God in prayer, and to the person in need.
3. It might be addictive
We think our lives are already full. Then we go lead worship at the women's prison, or serve a meal with an area feeding program, and God very clearly speaks a word to us: "You should do this every week, or even every day!" and we wonder how that could ever happen, given how over-committed we already are. Better to avoid volunteering altogether than put ourselves into situations where God might call something new and deeply sacrificial out of us.
4. Your life might never be the same
Every time I lead worship in the women's prison, on the drive home I have the same reflection: "That's the only real worship I attend or lead." I know, I know, real worship is about God and not our perceptions of what counts as true worship. Nevertheless, speaking a word of Christian freedom, going to a group of people and spending time with them because they are incarcerated and unable to come to you, doing this has the tendency to clarify the heart and mind, and teach us how much of what we call "worship" is actually our habitual practicing of privilege. We approach worship most of the time with a sense of entitlement--I deserve a worship service where the music is my style, where I will be fed by the message, and where I will like the experience. Go to church in jail, and suddenly everything old, everything normal, becomes supercharged with grace and meaning. Worship in that context is no longer about us and our privilege--it is about God and the people God loves and the word of hope and freedom God speaks to us in Christ.
As result, the next Sunday "normal" worship will seem so normal by comparison. Or at the very least, you'll be reminded that every worship service is preaching to those who are "in prison." Once again a good reason not to volunteer or go to the prison in the first place.
5. You might find out you have to change or learn something
The first time I had to visit patients on a hospital floor for my Clinical Pastoral Education, I was petrified. I didn't know what to say, had no idea how to visit people who were sick who I didn't already know. I needed to be equipped, and trained. Volunteering can challenge us in a similar way. We might find out we need to grow up, or go through therapy, or exercise, or learn a skill. As we all know, growing up, working on our emotional immaturities, skill building, and exercise are all hard work. Better to stay home and watch Comedy Central.
6. You'll be at risk of thinking volunteering is more important that the "normal" stuff you do every day
Sometimes when we volunteer we are tempted to think our volunteer service is more holy, or more important, than our daily vocations. We help people get nets to protect them from malaria in Africa, while we fail to protect the children in the school right next door, or shout at or neglect our own children. Charles Dickens in Bleak House tells the story of Mrs. Jellyby, who was so involved in mission work for Africa that she had no time for her own children or self-care. He writes, "Mrs Jellyby had very good hair, but was too much occupied with her African duties to brush it." Moral of the story: Don't end up like Mrs. Jellyby. Avoid volunteering like the plague, and just go home and brush your hair.
7. Your "holier than thou" detector might get recalibrated
While volunteering, it is easy to become self-righteous. Look across the street at that lazy slob out on his porch sunning himself and reading a paperback. Yes, you are so much better than that guy over there. You're volunteering, repairing the front door on a ministry that feeds people seven days a week. Right? Smile to yourself in your superiority, then remember, the next time the volunteer sheet is passed around, to skip writing your name down because next weekend YOU deserve to be out in your yard sunning. You did just volunteer last weekend, remember? You've earned your rest!