Sharing an excerpt from my article on Sadhana:
Sadhna, in general may refer to any effort/action (Karma) that is put
to achieve a specific goal. But in many Hindu philosophical
literatures, it specifically refers to any effort put to achieve a
spiritual goal. Literally the word “Sadhana” is derived from root word
“sadh” (to accomplish) and refers to any means or instrument to
accomplish a desired objective. Swami Chidananda of Divine Life
society defines sadhana as “the active effort to obtain that which is
possible of being obtained through effort”.
It is interesting to note that, even though sadhana includes rituals
and practices like mantra jap, havan, puja etc, it is usually assumed
to be confined only to them. But it is not so. Sadhna may refer to any
spiritual effort put by an individual. It may be a person deciding to
speak only truth, to lead a non-corrupt life or to remain celibate
throughout his life, all these are sadhna only. The key is, the effort
must be put with sincerity and must be practiced relentlessly.
Further, any activity practiced in harmony with surrounding nature and
the entire cosmos constitute a spiritual sadhana.
Every sadhna is an action i.e. Karma, hence many argue that no amount
of sadhna/karma can deliver enlightment as it can be attained only by
the grace of God and hence by surrendering to him. But this grace of
God is not randomly given; instead it dawns on only those who are
Adhikaari (competent) to receive it. The absolute dedication and
surrendering towards God does not come spontaneously to everyone.
Sadhana helps an individual to develop this surrender and dedication
and achieve the Adhikaara.
The goal of any spiritual sadhana is to increase concentration and
make the mind still. It helps to make an individual detached and
become Stitahprajna (stable/equilibrium). But this detachment is
neither disinterest towards objects of outer world nor apathy towards
people; instead it is pure selfless love for the whole cosmos without
any discrimination or selfish attachment. What actually Sadhana does
is to burn away the burden of past karmas that are blocking one’s
journey towards the source. Hence, the ultimate end result of any
spiritual Sadhana is Jnana (Enlightment) and complete merger with the
Read full article here- http://nithinsridhar.blogspot.in/2010/11/understanding-hinduism-sadhana.html
Regarding Yoga, here is another excerpt from one of my article-
Yoga literally means “Union” or “Conjunction”. Patanjali Yoga Sutra
(1.2-3) defines Yoga as a state wherein the patterns (vrittis) of the
mind has been removed or stilled, so that the “seer” (i.e. Atman, the
Witness) abides in his real nature”. Hence, yoga is a state of
Samadhi, wherein the Self or Atman has been isolated from the
limitations of Non-Self entities like body and mind so that the Atman
alone shines. This state is achieved by stilling the mind by causing
all the various thought-modifications of the mind to cease. Just as
various thoughts and dreams are products of modifications of
“manas/mind”. Similarly, from purely subjective perspective the
objective universe one perceives is also due to the modifications of
one’s mind. The Atman is the witness and the body and the mind are the
objects. Hence, when the mind is stilled and the modifications of mind
are brought into a stop, the objects merge into the subject and the
Atman which is the subject alone remains. This state of Samadhi is
called as “Yoga” or “Union” because there is a Union of duality of
object and subject giving rise to the non-dual abidance in Atman.
Read the full article on Yoga here- http://nithinsridhar.blogspot.in/2015/04/secularization-or-destruction-of-yoga.html
Tapas, in simple terms refers to Austerity, Self-control, spiritual practice and may at times be used as synonymous to Sadhana or Yoga as well. Here is another excerpt, from an article about how Menstruation is a period of Tapas:
But, first, let us examine the Hindu notion of Tapas. Hindu tradition
recognizes that some kind of Tapas is necessary to attain any
goal-sacred or secular- in life. In the simplest terms, Tapas refers
to austerity or hardship. Without facing hardships, without overcoming
obstacles, no work is accomplished. Recognizing this, the Hindu
scriptures have charted out how one can use this Tapas to attain
material welfare and spiritual emancipation.
At a deeper level, Tapas is defined as restrainment of the body, mind,
and the senses. And all austere practices and self-restrictions have
been laid out with an aim to achieve this restrainment. The stress on
sense-restrainment has been placed owing to the fact that only through
such a restrainment of the physical actions and the mental thoughts,
would a person be able to attain detachment and dispassion and free
oneself from the internal impurities like lust, anger, etc.
Thus, the scriptures declare that through Tapas, one destroys ones
impurities (of the body and mind) [Yoga Sutras of Patanjanli 2.43] and attains self-purification.
The importance of austerity in the Hindu tradition could be gauged by
the fact that, just like Shaucha, Tapas is also listed among the
Niyamas of Yoga [Yoga-Sutras of Patanjali 2.32]; among the basic Samanya Dharma; and is considered
vital for practicing Vedanta [Vivekachoodamani (Verse 22-23)].
Various Hindu rituals and practices have been designed with the
purpose to act as austerity to help one attain detachment and
self-purification. Beginning with Samskaras like Garbadhana (ceremony
marking the intention to give birth to a child) and Vivaha (marriage),
the daily ritual performances like that of Sandhyopasana, and various
kinds of vratas (vows of austerity, usually fasting) and pujas along
with their different rules and regulations that are performed
periodically, are all aimed to act as Tapas or ‘Austere practices’
that would help individuals to purify themselves and become free from
Adharmic (unrighteous) actions that they may have committed through
their body, mind, and speech- intentionally or unintentionally.
In other words, tapas not only aims to help an individual to become
free from some of the Adharmas committed in the past, but also helps
him/her to become detached and gain control over his/her senses and
thus helps in preventing him/her from committing more Adharma in
future. Hence, Austerity and self-purification play a very vital role
in aiding an individual in his journey towards the ultimate Moksha.
Here is the link to full article- http://indiafacts.org/hindu-view-of-menstruation-ii-menstruation-as-austerity-and-self-purification/