My son day trained at just over 2, but didn't lose the night diaper until 3 1/2. For naps, we just had him pee before going to sleep. At night, we stopped giving him water around 1 hour before bedtime, made him go to the bathroom before bed, and for him, it just wasn't until 3 1/2 that he started waking up dry. Once we saw a pattern of dryness, we motivated him to stay dry at night by giving him a toy for making it through 1 night, another for making it through the weekend (3 nights), and a final toy for making it 1 week (6 nights). By that point, he was fully trained.
Really, it was mostly because his bladder was finally big enough to last the whole night. The toys just helped motivate him to try.
We're in the process of training my 2 1/2 year old daughter. She has been enthusiastic and basically trained since 15 months, long before she was fully capable of undressing/redressing herself or even physically ready to train - she still peed every 15 minutes. I've really learned by comparing my experiences with her to those with my son that there is a large physical maturity aspect to this... So, hang in there. I swear when it is time, it will be easy.