There were a lot of hard things about serving a two year mission. Some things were harder than others. I didn't have a hard time living on a small budget. Fellow Elders would cut my hair most of the time (unless there was a salon nearby with cute hair dressers), so I seldom spent money on haircuts. We were fed dinner (tea) by members of the church most of the time so we rarely had to purchase dinner items. I got used to eating cereal with boxed milk (Seriously. Boxed milk.) for breakfast most mornings and beans on toast for most lunches. Not bad at all.
I'll tell you what the hardest part of serving a mission was. Are you ready? Serving with crappy companions. Oh my goodness it sucked so bad. Usually, in Dublin, it's typical for an Elder to stay in one area for 2-5 months, with the average being 3 or 4. For example, an Elder transfers to an area and gets placed with another Elder who has already been in the area for a month or two. The missionaries serve together for another month or two and then the missionary who's been there the longest transfers out and a new missionary replaces him. That's typically how it works, but there are exceptions all the time. I was one of the missionaries who transferred around more frequently than other missionaries. At the time, I remember being told by other Elders, "Oh, you're the missionary who gets along with everyone so Prez keeps putting you with Elders who have had previous personality conflicts." I was flattered until the last month or two of my mission when my companion said, "Oh, you're the missionary that everyone struggles to work with so you keep getting moved around." Uh... wait. Really? Maybe... but I really doubt that was the case. I only hated one of my companions.
Sometimes I complained about my companion. Occasionally when I would tell another missionary that I struggled with my comp, they'd reply with something like, "Well, a mission is kind of like a marriage, Elder. If you can't get along with a companion for a couple of months how do you expect to get along with your spouse for all eternity? You need to learn patience and understanding so you can use those same qualities to strengthen your marriage when the time comes."
The first few time I received this advice, I thought, "Oh, man. That's so true. I need to try harder to prayerfully seek the Spirit in this companionship." Until one day, I realized something. I get to PICK my wife. The mission president doesn't assign her to me. Hello? Putting up with a companion using my towel or not rinsing his whisker juice out of the sink after shaving is nothing like having a wife. Plus there's no sex to cancel out the disagreements with my companion (at least there's not supposed to be). When I marry someone, I get to do stuff to her. When I fought with my companion, the best I could hope for was sharing Ramen. Not the same... unless we're talking about 9 1/2 Weeks or something... and I'm not.