satkaaramaanapoojaartham tapo dambhena chaiva yat |
kriyate tadiha proktam raajasam chalamadhruvam || 18 ||

That which is performed for praise, honour, worship and ostentation, that praise is called raajasic, is said to be of this world, and is unstable and temporary.
satkaaraha : praise
maanaha : honour
poojaartham : for worship
tapaha : penance
dambhena : for ostentation
cha : and
eva : also
yat : that which
kriyate : performed
tat : that
iha : this world
proktam : is said to be
raajasam : raajasic
chalam : unstable
adhruvam : temporary
The Puraanaas are filled with stories of all kinds of demons who performed extremely severe penance and austerities. It is said that Raavana chopped off each of his ten heads until Lord Shiva granted him a boon. Hiranyakashipu performed such severe penance that his entire flesh dropped off and only his bones remained. However, none of these demons desired self realization or liberation as the outcome of their penance. They wanted some boon, some power such that they could vanquish their enemies.
Shri Krishna says that whenever we conserve our energy and put in a lot of effort towards any material goal, any goal which is “of this world”, such type of penance will be called raajasic. This penance could be for boosting our ego, in other words, for praise, honour, worship or for showing off. People spend years working extremely hard so that they can buy a fancy house or a car that can be shown off. Dictators do everything they can to ensure that people fall at their feet and worship them.
Ultimately, any effort that is expended towards an earthly goal will be temporary. A simple illustration to explain this notion is that of a ball thrown by a person in the air. No matter how hard the throw is, the ball will eventually fall down and stop moving. Furthermore, any result that we see in the world is also unstable. Several people go on crash diets that, in addition to giving temporary results, may actually harm the body. Any result in the material world is subject to the laws of Prakriti, to the three gunaas themselves, which are inherently unstable.