Health: In spite of getting all the vaccines you have and for having and taking half a pharmacy with you around the corner of your house, always - yes, always - you can catch a thousand things on a long trip through areas like South America, Asia or Africa, where the conditions of Health are not what we know in most of Europe. From malaria to large diarrhea through dengue. Always go with good health insurance to, if something happens to you, at least to be able to be treated in the best hospitals in the area.
Thefts: During my two long trips I suffered robberies. In the first one - from India to Bolivia - they robbed us on several occasions, being the worst in a place as unexpected as New Zealand, where they opened the trunk of our rented car and took everything we had, backpacks included. These setbacks are usually a strong blow to the morale of the troops but you always have to think that they are objects and money - except when your documents are also stolen, which complicates the thing a bit more - and while you are healthy, the rest can be arranged to continue travel.
Loneliness: many adventurous souls do not find that soulmate, or at least compatible, with whom to be able to embark on the dream adventure. In the end, many people end up traveling alone with the hope of mixing more intensely with the locals and meeting other travelers with whom to share conferences and experiences. Many times this happens but sometimes, due to the personality of the traveler or other circumstances, it is the case of having to spend long days of loneliness through unknown lands that can lead to a bit of downturn. It is true that there are people for everything and others who want to know themselves but, ultimately, ending up talking to your multi-purpose knife as if it had a life of its own, is not usually the goal of such a trip.
Post-depression depression: And you return home, where - except for strange cases of lucky or dad's children - you will have to return to the battered labor market and resume the life you left, or not. Because it may also be that the trip has changed your life and you decide to take a helm and live differently. But most return more or less to what he left. And while your friends ask you briefly and politely about the trip - remember this: they already have their life set up and most care little about your temporary departure from society normal- You try to do your best to find a place where your life does not become just an office, family and weekend getaways. You come from something very big and you don't want to lose the essence of what was experienced in this time. Remember: traveling is a virus and the more you travel the more you want to discover. After such a trip you will not be able to give up everything at once and you will have to fight for it.
Surely there are many more things that people will think of when they think of reasons not to embark on a great adventure but everyone has to weigh pros and cons when making such a decision.