Without wanting to have a go at the OP, whose affirmations that they did good deeds, made a difference etc I will take at face value, any prospective volunteer should at a minimum google 'voluntourism harmful' and read the other side of the volunteering argument before they go. There are some very worrying trends which point to the great harm which voluntourism can do- for example, in Cambodia there is a thriving trade in selling children to orphanages so that rich westerners can spend a few days 'volunteering' with orphans, even though 80% of children in some orphanages had at least one surviving parent. Not to mention the attachment issues which can form when young children are subjected to a conveyor belt of volunteers who arrive, form a bond with the children, and then leave weeks/months later.
This isn't to discredit what the OP may or may not have done, but anyone who volunteers should at the very least study both sides of the argument and decide for themselves whether their visit is likely to do more harm than good. 'Digging a well' is just taking a job and money away from a local manual labourer. 'Teaching English' in a country with a healthy supply of fluent English speaking locals (such as Ghana) may not be the best way to spend one's time- especially if you have no teaching experience.
It is interesting how so many comments on these volunteering threads focus on 'how much the experience must have changed the volunteer'- personal development is a nice byproduct of volunteering, but the primary purpose should always be to do good and to help people. By and large, this is best left to skilled workers (doctors at MSF, engineers at VSO etc.) as unskilled undergraduates are unlikely, in many cases, to be able to offer much of use.
Personal attacks aside, in the general sense I agree with the earlier poster. If people want to 'make a difference' then why not volunteer in the UK- or possibly in a less glamorous location (it's interesting how so many foreign volunteering placements are in 'easy' countries with wildlife, beaches, nice things to see and do- plenty of people go to Kenya, how many go to less glamorous Burundi where there is far greater need?)
I'm sure this particular individual made a difference/did good things etc. but it is worrying how many people here and elsewhere 'volunteer' for what is essentially a glorified holiday and make no effort to consider the potential harm that they may be causing to the communities they want to 'help'. This isn't just true of voluntourism- many professional development organisations arguably do more harm than good as well.