Can anybody help?

About 90% of the time (later in a tournament) when I'm a smallstack and I go allin a bigstack will call and I will loose. Most of the time I'm preflop ahead.

What should I do when the blinds is high and I have about only one or two rounds to go.

Should I go allin preflop with good cards or should I just raise big.

This is very frustrating as I normally go far in a tournament just to find me loosing to a bigstack.

Help help help!