1.) Truth (Satya)
2.) Pity (Daya)
3.) Penance (Tapa)
4.) Act of Giving (Daan)
Truth It means Righteousness. The Sat power within. If we are in flow with Truth substance of nature, what we say happens. We are not isolated. Nature does not think or the Truth substance present in Nature does not think us as a foreign body. So what we say happens. That is called Sat power or Satya. Lord Krishna says that a follower of Truth has to face lot of difficulties and has not a smooth life. Curses or blessings said from the depth of the heart becomes True because they are associated with the Truth substance of Nature.
Pity It means lack of insensitivity. Presence of Sensitivity. Not hard hearted.
Penance Usually living beings are engaged in sensual enjoyments. Penance area starts when hunger force is at its peak. Desire to see, hear, taste etc is intense. When such desires are obstructed by will power, the resultant force or pressure generated is called Penance. Penance increases magnetism and nature forces whirl around that soul to satisfy that soul and bring it back to equilibrium. Intense Penance may lead to loss of mind balance says Lord Krishna in SrimadBhagvat. Penance is done to become the master of senses and sensual enjoyments. In absence of Penance, a person is slave to senses. However he or she never realises it until they are caught in a desert or some isolated place. As per some facts, when a plane crashed in cold place, a person survived by eating human bodies. Those not practicing Penance undergo such stages that they do such things to survive. A Penanceful person on the contrary will meditate in Lord Sun or prefer to die rather than eating human bodies and survive. Hence Penance is essential to lift a human from animal level tendencies. Those who have studied about Carl Jung or the Russian experiments where they put hand in hot sand and assume it in ice and puts another hand in ice and assumes it in hot sand etc. very well knows the impact of Penance, mind power etc.
Act of Giving This means donation. But this can be giving money or food or knowledge or anything else. Vaishnavs are devotees of Lord Vishnu who is Preserver or Paalanhaar. Hence every devotee likes to help Lord Vishnu by donating ie assisting in Paalan Dharma of Lord Vishnu.