1. Even if you fail often, you do suceed once in a while. The persistent simply take more chances and win more times than those that don't.
2. Some crutches are only slowing you down (i.e. marking bombs instead of keeping a mental count of bomb placement), but in a few cases they can save you (e.g. getting an estimate of remaining bombs can help one play odds in her/his favor). Lean on friends and family once in while.
3. In some cases, you keep getting the same scenario (either at local level or at a grander scale), so by playing a lot you might get to recognize them and make the right move.
4. Sometimes you keep repeating your mistake even when you know better (e.g. uncovering bomb instead of marking it when rushing it and not paying close attention, or when miscounting adjacent bombs). Make sure to slow down, pay attention and double count before making important decisions.
5. It is always better to eliminate guessing if possible, but there will always be times when guessing is unavoidable. Make pure guesses earlier if possible to avoid the dissappointment when you are wrong (instead of later after much time and sweat was already invested).